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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..d7b82bc --- /dev/null +++ b/.gitattributes @@ -0,0 +1,4 @@ +*.txt text eol=lf +*.htm text eol=lf +*.html text eol=lf +*.md text eol=lf diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..6312041 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,11 @@ +This eBook, including all associated images, markup, improvements, +metadata, and any other content or labor, has been confirmed to be +in the PUBLIC DOMAIN IN THE UNITED STATES. + +Procedures for determining public domain status are described in +the "Copyright How-To" at https://www.gutenberg.org. + +No investigation has been made concerning possible copyrights in +jurisdictions other than the United States. Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..a80b4ba --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #64380 (https://www.gutenberg.org/ebooks/64380) diff --git a/old/64380-0.txt b/old/64380-0.txt deleted file mode 100644 index 300092a..0000000 --- a/old/64380-0.txt +++ /dev/null @@ -1,4771 +0,0 @@ -The Project Gutenberg eBook of The fauna of the deep sea, by Sydney John -Hickson - -This eBook is for the use of anyone anywhere in the United States and -most other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms -of the Project Gutenberg License included with this eBook or online at -www.gutenberg.org. If you are not located in the United States, you -will have to check the laws of the country where you are located before -using this eBook. - -Title: The fauna of the deep sea - -Author: Sydney John Hickson - -Release Date: January 24, 2021 [eBook #64380] - -Language: English - -Character set encoding: UTF-8 - -Produced by: Richard Tonsing, Sharon Joiner, Bryan Ness, and the Online - Distributed Proofreading Team at https://www.pgdp.net (This - file was produced from images generously made available by The - Internet Archive/American Libraries.) - -*** START OF THE PROJECT GUTENBERG EBOOK THE FAUNA OF THE DEEP SEA *** - - - =Modern Science Series= - - _EDITED BY SIR JOHN LUBBOCK, BART., M. P._ - - - - - THE FAUNA OF THE DEEP SEA - - -[Illustration: STOMIAS BOA. HALF NATURAL SIZE. FROM A DEPTH OF 1,900 -METRES. (AFTER FILHOL.)] - - - - - THE FAUNA OF THE DEEP SEA - - - BY - - SYDNEY J. HICKSON, M. A. - (CANTAB. ET OXON.) - D.SC. (LOND.), FELLOW OF DOWNING COLLEGE, CAMBRIDGE - - - _WITH TWENTY-THREE ILLUSTRATIONS_ - -[Illustration] - - NEW YORK - D. APPLETON AND COMPANY - 1894. - - - - - _Authorized Edition._ - - - - - PREFACE - - -The time may come when there will be no portion of the earth’s surface -that has not been surveyed and explored by man. - -The work of enterprising travellers has now been carried on within a -measurable distance of the North Pole; the highest mountain ranges are -gradually succumbing to the geological surveyor; the heart of Africa is -giving up to us its secrets and its treasures, and plans of all the -desert places of the earth are being made and tabulated. - -The bottom of the deep sea was until quite recently one of these terræ -incognitæ. It was regarded by most persons, when it entered into their -minds to consider it at all, as one of those regions about which we do -not know anything, never shall know anything, and do not want to know -anything. - -But the men of science fifty years ago were not disposed to take this -view of the matter. Pushing their inquiries as to the character of the -sea-fauna into deeper and deeper water, they at length demanded -information as to the existence of forms of animal life in the greatest -depths. Unable themselves to bear the heavy expenses involved in such an -investigation, they sought for and obtained the assistance of the -Government, in the form of national ships, for the work, and then our -knowledge of the depths of the great ocean may be said to have -commenced. - -We know a good deal now, and in the course of time we may know a great -deal more, about this interesting region; but it is not one which, in -our generation at any rate, any human being will ever visit. - -We may be able to plant the Union Jack on the summit of Mount Everest, -we may drag our sledges to the South Pole, and we may, some day, be able -to travel with ease and safety in the Great Sahara; but we cannot -conceive that it will ever be possible for us to invent a diving-bell -that will take a party of explorers to a depth of three and a half miles -of water. We may complete our survey of the ocean beds, we may analyse -the bottom muds and name and classify the animals that compose their -fauna, but there are many things that must remain merely matters of -conjecture. We shall never know, for example, with any degree of -certainty, how _Bathypterois_ uses its long feeler-like pectoral fins, -nor the meaning of the fierce armature of _Lithodes ferox_; why the -deep-sea Crustacea are so uniformly coloured red, or the intensity of -the phosphorescent light emitted by the Alcyonaria and Echinoderms. -These and many others are and must remain among the mysteries of the -abyss. - -Our present-day knowledge of the physical conditions of the bottom of -the deep sea and the animals that dwell there is by no means -inconsiderable. - -It may be found in the reports of the scientific expeditions fitted out -by the English, French, German, Italian, Norwegian, and American -Governments, in numerous volumes devoted to this kind of work, and in -memoirs and notes scattered through the English and foreign scientific -journals. - -It is the object of this little book to bring together in a small -compass some of the more important facts and considerations that may be -found in this great mass of literature, and to present them in such a -form that they may be of interest to those who do not possess a -specialist’s knowledge of genera and species. - -When it was found that animals can and do live even at the greatest -depths of the ocean, the interest of naturalists was concentrated on the -solution of the following problems. Firstly, do the animals constituting -the fauna of the abyss exhibit any striking and constant modification in -correlation with the physical conditions of their strange habitat? And, -secondly, from what source was the fauna of the abyss derived? Was it -derived from the shallow shore waters, or from the surface of the sea? -Is it of very ancient origin, or the result of, comparatively speaking, -recent immigrations? - -These questions cannot be answered in a few lines. Any views that may be -put forward regarding them require the support of a vast array of facts -and figures; but as the limits of this little book would not permit of -my giving these, I have endeavoured to select a few only of those which -bear most directly upon the points at issue. - -To overburden my work with the names of genera or the lists of species -would not, it seemed to me, either clear the issues or interest the -general reader. These may be found in the ‘Challenger’ monographs, and -other books dealing with the subject. - -Those who wish to pursue the subject further will find in the ‘Voyages -of the “Blake,”’ by Alexander Agassiz, an excellent and elaborate -discussion of deep-sea problems, and numerous illustrations of some of -the most interesting forms of abysmal life. - -In Volume XXIII. of the ‘Bulletin of Comparative Zoology’ the same -author gives a most interesting account of the deep-sea work that has -recently been done by the ‘Albatross’ expedition. - -Filhol’s ‘La Vie au Fond des Mers’ is also a book that contains a great -deal of new and interesting matter, together with some excellent -coloured plates of deep-sea animals. - - SYDNEY J. HICKSON. - - DOWNING COLLEGE, CAMBRIDGE: - _September, 1893_. - - - - - CONTENTS - - - CHAPTER PAGE - I. A SHORT HISTORY OF THE INVESTIGATIONS 1 - - II. THE PHYSICAL CONDITIONS OF THE ABYSS 17 - - III. THE RELATIONS OF THE ABYSMAL ZONE AND THE ORIGIN OF ITS - FAUNA 45 - - IV. THE CHARACTERS OF THE DEEP-SEA FAUNA 59 - - V. THE PROTOZOA, CŒLENTERA, AND ECHINODERMA OF THE DEEP SEA 86 - - VI. THE VERMES AND MOLLUSCA OF THE DEEP SEA 109 - - VII. THE ARTHROPODA OF THE DEEP SEA 123 - - VIII. THE FISH OF THE DEEP SEA 148 - - INDEX 167 - - - - - LIST OF ILLUSTRATIONS - - - STOMIAS BOA. AFTER FILHOL, ‘LA VIE AU FOND DES - MERS’ _Frontispiece_ - - FIG. PAGE - 1 DIAGRAM ILLUSTRATING THE PASSAGE OF AN OCEAN - CURRENT ACROSS A BARRIER 32 - - 2 _Sicyonis crassa._ AFTER HERTWIG, ‘“CHALLENGER” - REPORTS’ 36 - - 3 GLOBIGERINA OOZE. AFTER AGASSIZ, ‘VOYAGES OF THE - “BLAKE”’ 38 - - 4 SECTION THROUGH THE EYE OF _Serolis schythei_. - AFTER BEDDARD, ‘“CHALLENGER” REPORTS’ 74 - - 5 SECTION THROUGH THE EYE OF _Serolis bromleyana_. - AFTER BEDDARD, ‘“CHALLENGER” REPORTS’ 74 - - 6 _Opostomias micripnus._ AFTER GÜNTHER, - ‘“CHALLENGER” REPORTS’ 78 - - 7 HEAD OF _Pachystomias microdon_. AFTER VON - LENDENFELD, ‘“CHALLENGER” REPORTS’ 79 - - 8 SECTION THROUGH THE ANTERIOR SUB-ORBITAL - PHOSPHORESCENT ORGAN OF _Pachystomias microdon_. - AFTER VON LENDENFELD, ‘“CHALLENGER” REPORTS’ 80 - - 9 _Challengeria Murrayi._ AFTER HAECKEL, - ‘“CHALLENGER” REPORTS’ 90 - - 10 _Umbellula Güntheri._ AFTER AGASSIZ, ‘VOYAGES OF - THE “BLAKE”’ 97 - - 11 _Rhizocrinus lofotensis._ AFTER CARPENTER, - ‘“CHALLENGER” REPORTS’ 100 - - 12 _Rhabdopleura normani._ AFTER LANKESTER, - ‘CONTRIBUTIONS TO OUR KNOWLEDGE OF RHABDOPLEURA - AND AMPHIOXUS’ 112 - - 13 A SINGLE POLYPIDE OF _Rhabdopleura normani_. AFTER - LANKESTER, _tom. cit._ 114 - - 14 _Bathyteuthis abyssicola._ AFTER HOYLE, - ‘“CHALLENGER” REPORTS’ 121 - - 15 _Bathynomus giganteus._ AFTER FILHOL, _tom. cit._ 131 - - 16 _Euphausia latifrons._ AFTER SARS, ‘“CHALLENGER” - REPORTS’ 134 - - 17 _Bentheuphausia amblyops._ AFTER SARS, - ‘“CHALLENGER” REPORTS’ 134 - - 18 _Polycheles baccata._ AFTER SPENCE BATE, - ‘“CHALLENGER” REPORTS’ 136 - - 19 _Colossendeis arcuatus._ AFTER FILHOL, _tom. cit._ 141 - - 20 _Hypobythius calycodes._ AFTER MOSELEY, - ‘“CHALLENGER” REPORTS’ 145 - - 21 _Melanocetus Murrayi._ AFTER GÜNTHER, - ‘“CHALLENGER” REPORTS’ 156 - - 22 _Saccopharynx ampullaceus._ AFTER GÜNTHER, - ‘“CHALLENGER” REPORTS’ 164 - - - - - THE FAUNA OF THE DEEP SEA - - - - - CHAPTER I - A SHORT HISTORY OF THE INVESTIGATIONS - - -Our knowledge of the natural history of the deep seas may be said to -have commenced not more than fifty years ago. There are, it is true, a -few fragments of evidence of a fauna existing in depths of more than a -hundred fathoms to be found in the writings of the earlier navigators, -but the methods of deep-sea investigation were so imperfect in those -days that naturalists were disposed to believe that in the abysses of -the great oceans life was practically non-existent. - -Even Edward Forbes just before his death wrote of an abyss ‘where life -is either extinguished or exhibits but a few sparks to mark its -lingering presence,’ but in justice to the distinguished naturalist it -should be remarked that he adds, ‘Its confines are yet undetermined, and -it is in the exploration of this vast deep-sea region that the finest -field for submarine discovery yet remains.’ - -Forbes was only expressing the general opinion of naturalists of his -time when he refers with evident hesitation to the existence of an azoic -region. His own dredging excursions in depths of over one hundred -fathoms proved the existence of many peculiar species that were -previously unknown to science. ‘They were like,’ he says, ‘the few stray -bodies of strange red men, which tradition reports to have been washed -on the shores of the Old World before the discovery of the New, and -which served to indicate the existence of unexplored realms inhabited by -unknown races, but not to supply information about their character, -habits, and extent.’ - -In the absence of any systematic investigation of the bottom of the deep -sea, previous to Forbes’s time the only information of deep-sea animals -was due to the accidental entanglement of certain forms in sounding -lines, or to the minute worms that were found in the mud adhering to the -lead. - -As far back as 1753, Ellis described an Alcyonarian that was brought up -by a sounding line from a depth of 236 fathoms within eleven degrees of -the North Pole by a certain Captain Adriaanz of the ‘Britannia.’ The -specimen was evidently an _Umbellula_, and it is stated that the arms -(i.e. Polyps) were of a bright yellow colour and fully expanded when -first brought on deck. - -In 1819 Sir John Ross published an account of his soundings in Baffin’s -Bay, and mentions the existence of certain worms in the mud brought from -a depth of 1,000 fathoms, and a fine Caput Medusæ (Astrophyton) -entangled on the sounding line at a depth of 800 fathoms. - -In the narrative of the voyage of the ‘Erebus’ and ‘Terror,’ published -in 1847, Sir James Ross calls attention to the existence of a deep-sea -fauna, and makes some remarks on the subject that in the light of modern -knowledge are of extreme interest. ‘I have no doubt,’ he says, ‘that -from however great a depth we may be enabled to bring up the mud and -stones of the ocean, we shall find them teeming with animal life.’ This -firm belief in the existence of an abysmal fauna was not, as it might -appear from the immediate context of the passage I have quoted, simply -an unfounded speculation on his part, but was evidently the result of a -careful and deliberate chain of reasoning, as may be seen from the -following passage that occurs in another part of the same book:—‘It is -well known that marine animals are more susceptible of change of -temperature than land animals; indeed they may be isothermally arranged -with great accuracy. It will, however, be difficult to get naturalists -to believe that these fragile creatures could possibly exist at the -depth of nearly 2,000 fathoms below the surface; yet as we know they can -bear the pressure of 1,000 fathoms, why may they not of two? We also -know that several of the same species of creatures inhabit the Arctic -that we have fished up from great depths in the Antarctic seas. The only -way they could get from one pole to the other must have been through the -tropics; but the temperature of the sea in those regions is such that -they could not exist in it, unless at a depth of nearly 2,000 fathoms. -At that depth they might pass from the Arctic to the Antarctic Ocean -without a variation of five degrees of temperature; whilst any land -animal, at the most favourable season, must experience a difference of -fifty degrees, and, if in the winter, no less than 150 degrees of -Fahrenheit’s thermometer—a sufficient reason why there are neither -quadrupeds, nor birds, nor land insects common to both regions.’ - -In the year 1845, Goodsir succeeded in obtaining a good haul in Davis -Straits, at a depth of 300 fathoms. It included Mollusca, Crustacea, -Asterids, Spatangi, and Corallines. - -In 1848, Lieutenant Spratt read a paper at the meeting of the British -Association at Swansea, on the influence of temperature upon the -distribution of the fauna in the Ægean seas, and at the close of this -paper we find the following passage, confirming in a remarkable way the -work of previous investigators in the same field. He says: ‘The greatest -depth at which I have procured animal life is 390 fathoms, but I believe -that it exists much lower, although the general character of the Ægean -is to limit it to 300 fathoms; but as in the deserts we have an oasis, -so in the great depths of 300, 400, and perhaps 500 fathoms we may have -an oasis of animal life amidst the barren fields of yellow clay -dependent upon favourable and perhaps accidental conditions, such as the -growth of nullipores, thus producing spots favourable for the existence -and growth of animal life.’ - -The next important discovery was that of the now famous Globigerina mud -by Lieutenants Craven and Maffit, of the American Coast survey, in 1853, -by the help of the sounding machine invented by Brooke. This was -reported upon by Professor Bailey. - -Further light was thrown upon the deep-sea fauna by Dr. Wallich in 1860, -on board H.M.S. ‘Bulldog’, by the collection of thirteen star-fish -living at a depth of 1,260 fathoms. - -Previous to this Torell, during two excursions to the Northern seas, had -proved the existence of an extensive marine fauna in 300 fathoms, and -had brought up with the ‘Bulldog’ machine many forms of marine -invertebrates from depths of over 1,000 fathoms; but it was not until -1863, when Professor Lovén read a report upon Torell’s collections, that -these interesting and valuable investigations became known to -naturalists. - -Nor must mention be omitted of the remarkable investigations of Sars and -his son, the pioneers of deep-sea zoology on the coasts of Norway, who, -by laborious work commenced in 1849, failed altogether to find any -region in the deep water where animal life was non-existent, and indeed -were the first to predict an extensive abysmal fauna all over the floor -of the great oceans. One of the many remarkable discoveries made by Sars -was _Rhizocrinus_, a stalked Crinoid. - -Ever since that time the Norwegians and the Swedes have been most -energetic in their investigations, and the publications of the results -of the Norske Nord-havns expeditions are regarded by all naturalists as -among the most valuable contributions to our knowledge of the deep-sea -fauna. - -Notwithstanding the previous discovery of many animals that undoubtedly -came from the abysmal depths of the ocean, there were still some persons -who found a difficulty in believing that animal life could possibly -exist under the enormous pressure of these great depths. It was -considered to be more probable that these animals were caught by the -dredge or sounding lines in their ascent or descent; and that they were -merely the representatives of a floating fauna living a few fathoms -below the surface. - -The first direct proof of the existence of an invertebrate fauna in deep -seas was found by the expedition that was sent to repair the submarine -cable of the Mediterranean Telegraph Company. The cable had broken in -deep water, and a ship was sent out to examine and repair the damage. -When the broken cable was brought on deck, it bore several forms of -animal life that must have become attached to it and lived at the bottom -of the sea in water extending down to a depth of 1,200 fathoms. Among -other forms a _Caryophyllia_ was found attached to the cable at 1,100 -fathoms, an oyster (_Ostrea cochlear_), two species of Pecten, two -gasteropods, and several worms. - -The discoveries that had been made indicating the existence of a -deep-sea fauna led to the commission of H.M. ships ‘Lightning’ and -‘Porcupine,’ and the systematic investigation that was made by the -naturalists on these vessels brought home to the minds of naturalists -the fact that there is not only an abysmal fauna, but that in places -this deep-sea fauna is very rich and extensive. The ‘Lightning’ was -despatched in the spring of 1868 and carried on its investigations in -the neighbourhood of the Faeroe Islands, but the vessel was not suitable -for the purpose and met with bad weather. The results, however, were of -extreme importance; for, besides solving many important points -concerning the distribution of ocean temperature, ‘it had been shown -beyond question that animal life is both varied and abundant at depths -in the ocean down to 650 fathoms at least, notwithstanding the -extraordinary conditions to which animals are there exposed.’ - -Among the remarkable animals dredged by the ‘Lightning’ were the curious -Echinoderm, _Brisinga coronata_, previously discovered by Sars, and the -Hexactinellid sponges, _Holtenia_ and _Hyalonema_, the Crinoids -_Rhizocrinus_ and _Antedon celticus_, and the Pennatulid _Bathyptilum -Carpenteri_, not to mention numerous Foraminifera new to science. - -In the spring of the following year, 1869, the Lords Commissioners of -the Admiralty despatched the surveying vessel ‘Porcupine’ to carry on -the work commenced by the ‘Lightning.’ - -The first cruise was on the west coast of Ireland, the second cruise to -the Bay of Biscay, where dredging was satisfactorily carried on to a -depth of 2,435 fathoms, and the third in the Channel between Faeroe and -Scotland. - -The dredging in 2,435 fathoms was quite successful, and the dredge -contained several Mollusca, including new species of _Dentalium_, -_Pecten_, _Dacrydium_, &c., numerous Crustacea and a few Annelids and -Gephyrea, besides Echinoderma and Protozoa. A satisfactory dredging was -also made in 1,207 fathoms. - -The third cruise was also successful and brought many new species to -light, including the _Porocidaris purpurata_, and a remarkable heart -urchin, _Pourtalesia Jeffreysi_. - -Concerning Pourtalesia Sir Wyville Thomson says:— - -‘The remarkable point is that, while we had so far as we were aware no -living representative of this peculiar arrangement of what is called -“disjunct” ambulacra, we have long been acquainted with a fossil -family—the Dysasteridæ—possessing this character. Many species of the -genera Dysaster, Collyrites, &c., are found from the lower oolite to the -white chalk, but there the family had previously been supposed to have -become extinct.’ - -The discovery of two new Crinoids led to the anticipation that the -Crinoidea, the remarkable group of Echinoderma, supposed at the time to -be on the verge of extinction, probably form rather an important element -in the abysmal fauna. - -One of the most interesting results was the discovery of three genera in -deep water, _Calveria_, _Neolampas_ and _Pourtalesia_, almost -immediately after they were discovered by Pourtales in deep water on the -coasts of Florida, showing thus a wide lateral distribution and -suggesting a vast abysmal fauna. - -A year before the ‘Lightning’ was despatched, Count Pourtales had -commenced a series of investigations of the deep-sea fauna off the coast -of Florida. The first expedition started in 1867 from Key West for the -purpose of taking some dredgings between that port and Havana. -Unfortunately yellow fever broke out on board soon after they started, -and only a few dredgings were taken. However, the results obtained were -of such importance that they encouraged Pourtales to undertake another -expedition and enabled him to say very positively ‘that animal life -exists at great depths, in as great a diversity and as great an -abundance as in shallow water.’ - -In the following years, 1868 and 1869, the expeditions were more -successful, and many important new forms were found in water down to 500 -fathoms. Perhaps the most interesting result obtained was the discovery -of _Bourguetticrinus_ of D’Orbigny; it may even be the species named by -him which occurs fossil in a recent formation in Guadeloupe. - -By this time the interest of scientific men was thoroughly excited over -the many problems connected with this new field of work. The prospect of -obtaining a large number of new and extremely curious animals, the faint -hope that living Trilobites, Cystids, and other extinct forms might be -discovered, and lastly the desire to handle and investigate great masses -of pure protoplasm in the form of the famous but unfortunately -non-existent Bathybius, induced some men of wealth and leisure to spend -their time in deep-sea dredging, and stimulated the governments of some -civilised countries to lend their aid in the support of expeditions for -the deep-sea survey. - -Mr. Marshall Hall’s yacht, the ‘Norma,’ was employed for some time in -this work, and an extensive collection of deep-sea animals was made. -About the same time Professor L. Agassiz was busy on board the American -ship, the ‘Hassler,’ in continuing the work of Count Pourtales, and -later on the Germans fitted out the ‘Gazelle,’ and the French the still -more famous ‘Travailleur’ and ‘Talisman’ expeditions. Nor must we omit -to mention in this connection the cruise of the Italian vessel, the -‘Vittor Pessani,’ nor those of the British surveying vessels, the -‘Knight Errant’ and the ‘Triton,’ and the American vessels, ‘The Blake’ -and the ‘Fish Hawk.’ - -But of all these expeditions, by far the most complete in all the -details of equipment, and the arrangements made for the publication of -the results, was the expedition fitted out in 1873 by the British -Government. The voyage of H.M.S. ‘Challenger’ is so familiar to all who -take an interest in the progress of scientific discovery, that it is not -necessary to do more than make a passing mention of it in this place. -The excellent books that were written by Wyville Thomson, by Moseley, -and by other members of the staff, have made the general reader familiar -with the narrative of that remarkable cruise and the most striking of -the many scientific discoveries that were made; while the numerous large -monographs that have been published during the past fourteen years give -opportunities to the naturalist of obtaining all the requisite -information concerning the detailed results of the expedition. - -The expenditure of the large sum of money upon this expedition and the -publication of its reports has been abundantly justified. The -information obtained by the ‘Challenger’ will be for many years to come -the nucleus of our knowledge of the deep-sea fauna, the centre around -which all new facts will cluster, and the guide for further -investigations. - -To say that the ‘Challenger’ accomplished all that was expected or -required would be to over-estimate the value of this great expedition, -but nevertheless it is difficult for us, even now, thoroughly to grasp -the importance of the results obtained or to analyse and classify the -numerous and very remarkable facts that were gained during her four -years’ cruise. - -It is, of course, impossible, in a few lines, to give a summary of the -more important of the Natural History results of the ‘Challenger’ -expedition. Besides proving the existence of a fauna in the sea at all -depths and in all regions, the expedition further proved that the -abysmal fauna, taken as a whole, does not possess characters similar to -those of the fauna of any of the secondary or even tertiary rocks. A few -forms, it is true, known to us up to that time only as fossils, were -found to be still living in the great depths, but a large majority of -the animals of these regions were found to be new and specially modified -forms of the families and genera inhabiting shallow waters of modern -times. No Trilobites, no Blastoids, no Cystoids, no new Ganoids, and -scarcely any deep-sea Elasmobranchs were brought to light, but the fauna -was found to consist mainly of Teleosteans, Crustacea, Cœlentera, and -other creatures unlike anything known to have existed in Palæozoic -times, specially modified in structure for their life in the great -depths of the ocean. - -In 1876 the S.S. ‘Vöringin’ was chartered by the Norwegian Government -and was dispatched to investigate the tract of ocean lying between -Norway, the Faeroe islands, Jan Mayen, and Spitzbergen. The -investigations extended over three years, the vessel returning to Bergen -in the winter months. - -The civilian staff of the ‘Vöringin’ included Professors H. Mohn, -Danielssen, and G. O. Sars, and the expedition was successful in -obtaining a large number of animals from deep water by means of the -dredge and tangles and by the trawl. - -The results of this expedition have been published in a series of large -quarto volumes under the general title of the Norske Nord-havns -Expedition. - -The most interesting forms brought to light by the Norwegians are the -two genera _Fenja_ and _Aegir_, animals possessing the general form of -sea anemones but distinguished from all Cœlenterates by the presence of -a continuous and straight gut reaching from the mouth to the aboral -pores which completely shuts off the cœlenteron or general body cavity -from the stomodæum. - -In more recent times the work has been by no means neglected. With the -advantage of employing many modern improvements in the dredges and -trawls in use, the American steamer, the ‘Albatross,’ has been engaged -in a careful investigation of the deep-sea fauna of the eastern slopes -of the Pacific Ocean, while at the same time Her Majesty’s surveying -vessel, the ‘Investigator,’ has been obtaining some interesting and -valuable results from a survey of the deep waters of the Indian Ocean. -But our knowledge of this vast and wonderful region is still in its -infancy. We have gathered, as it were, only a few grains from a great -unknown desert. It is true that we may not for many years, if ever, -obtain any results that will cause the same deep interest and excitement -to the scientific public as those obtained by the first great national -expeditions, but there are still many important scientific problems that -may be and will be solved by steady perseverance in this field of work, -and if we can only obtain the same generous support from public -institutions and from those in charge of national funds that we have -received in the past two decades, many more important facts will -doubtless be brought to light. - - - - - CHAPTER II - THE PHYSICAL CONDITIONS OF THE ABYSS - - -It is not surprising that the naturalists of the early part of the -present century could not believe in the existence of a fauna at the -bottom of the deep seas. - -The extraordinary conditions of such a region—the enormous pressure, the -absolute darkness, the probable absence of any vegetable life from want -of direct sunlight—might very well have been considered sufficient to -form an impassable barrier to the animals migrating from the shallow -waters and to prevent the development of a fauna peculiarly its own. - -The fragmentary accounts of animals brought up by sounding lines from -great depths might, it is true, have thrown doubts on the current views; -but they were not of sufficient importance in themselves, nor were the -observations made with such regard to the possibility of error, as to -withstand the critical remarks that were made to explain them away. - -The absence of any evidence obtained by accurate systematic research, -together with the consideration of the physical character of the ocean -bed, were quite sufficient to lead scientific men of that period to -doubt the existence of any animal life in water deeper than a few -hundred fathoms. - -We now know, however, that there is a very considerable fauna at -enormous depths in all the great oceans, and we have acquired, moreover, -considerable information concerning some of those peculiar physical -conditions of the abyss that fifty years ago were merely matters of -speculation among scientific men. - -The relation between animals and their environment is now a question of -such great interest and importance that it is necessary in any -description of the fauna of a particular region to consider its physical -conditions and the influence that it may be supposed to have had in -producing the characteristics of the fauna. - -The peculiar physical conditions of the deep seas may be briefly stated -to be these: It is absolutely dark so far as actual sunlight is -concerned, the temperature is only a few degrees above freezing point, -the pressure is enormous, there is little or no movement of the water, -the bottom is composed of a uniform fine soft mud, and there is no plant -life. - -All of these physical conditions we can appreciate except the enormous -pressure. Absolute darkness we know, the temperature of the deep seas is -not an extraordinary one, the absence of movement in the water and the -fine soft mud are conditions that we can readily appreciate; but the -pressure is far greater than anything we can realise. - -At a depth of 2,500 fathoms the pressure is, roughly speaking, two and a -half tons per square inch—that is to say, several times greater than the -pressure exerted by the steam upon the piston of our most powerful -engines. Or, to put the matter in other words, the pressure per square -inch upon the body of every animal that lives at the bottom of the -Atlantic Ocean is about twenty-five times greater than the pressure that -will drive a railway train. - -A most beautiful experiment to illustrate the enormous force of this -pressure was made during the voyage of H.M.S. ‘Challenger.’ I give the -description of it in the words of the late Professor Moseley. - -‘Mr. Buchanan hermetically sealed up at both ends a thick glass tube -full of air, several inches in length. He wrapped this sealed tube in -flannel, and placed it, so wrapped up, in a wide copper tube, which was -one of those used to protect the deep-sea thermometers when sent down -with the sounding apparatus. - -‘This copper tube was closed by a lid fitting loosely, and with holes in -it, and the copper bottom of the tube similarly had holes bored through -it. The water thus had free access to the interior of the tube when it -was lowered into the sea, and the tube was necessarily constructed with -that object in view, in order that in its ordinary use the water should -freely reach the contained thermometer. - -‘The copper case containing the sealed glass tube was sent down to a -depth of 2,000 fathoms and drawn up again. It was then found that the -copper wall of the case was bulged and bent inwards opposite the place -where the glass tube lay, just as if it had been crumpled inward by -being violently squeezed. - -‘The glass tube itself, within its flannel wrapper, was found when -withdrawn, reduced to a fine powder, like snow almost. What had happened -was that the sealed glass tube, when sinking to gradually increasing -depths, had held out long against the pressure, but this at last had -become too great for the glass to sustain, and the tube had suddenly -given way and been crushed by the violence of the action to a fine -powder. So violent and rapid had been the collapse that the water had -not had time to rush in by means of the holes at both ends of the copper -cylinder and thus fill the empty space left behind by the collapse of -the glass tube, but had instead crushed in the copper wall and brought -equilibrium in that manner. The process is exactly the reverse of an -explosion, and is termed by Sir Wyville Thomson an “implosion.”’ - -It is but reasonable to suppose that the ability to sustain this -enormous pressure can only be acquired by animals after generations of -gradual migrations from shallow waters. Those forms that are brought up -by the dredge from the depths of the ocean are usually killed and -distorted by the enormous and rapid diminution of pressure in their -journey to the surface, and it is extremely probable that shallow-water -forms would be similarly killed and crushed out of shape were they -suddenly plunged into very deep water. The fish that live at these -enormous depths are in consequence of the enormous pressure liable to a -curious form of accident. If, in chasing their prey or for any other -reason, they rise to a considerable distance above the floor of the -ocean, the gases of their swimming bladder become considerably expanded -and their specific gravity very greatly reduced. Up to a certain limit -the muscles of their bodies can counteract the tendency to float upwards -and enable the fish to regain its proper sphere of life at the bottom; -but beyond that limit the muscles are not strong enough to drive the -body downwards, and the fish, becoming more and more distended as it -goes, is gradually killed on its long and involuntary journey to the -surface of the sea. The deep-sea fish, then, are exposed to a danger -that no other animals in this world are subject to, namely that of -tumbling upwards. - -That such accidents do occasionally occur is evidenced by the fact that -some fish, which are now known to be true deep-sea forms, were -discovered dead and floating on the surface of the ocean long before our -modern investigations were commenced. - -Until quite recently, every one agreed that no rays of sunlight could -possibly penetrate the sea to a greater depth than a few hundred -fathoms. - -Moseley says that ‘probably all is dark below 200 fathoms excepting in -so far as light is given out by phosphorescent animals,’ and Wyville -Thomson speaks of the ‘utter darkness of the deep-sea bottom.’ - -Within the last few years a few authors have maintained that it is quite -possible that a few rays of sunlight do penetrate even to the greatest -depths of the ocean—a view mainly based on the fact that so many -deep-sea animals possess extremely perfect and complicated eyes and very -brilliant colours. Verrill says: ‘It seems to me probable that more or -less sunlight does actually penetrate to the greatest depths of the -ocean, in the form of a soft sea-green light, perhaps at 2,000 or 3,000 -fathoms equal in intensity to our partially moonlight nights and -possibly at the greatest depths equal only to starlight. It must be -remembered that in the deep sea far away from land the water is far more -transparent than near the coast.’ Packard is of a similar opinion. - -There seem to me to be very slight grounds for this view. The fact that, -comparatively speaking, shallow-water fish avoid nets that are rendered -phosphorescent by entangled jelly-fish does not justify us in assuming -that deep-sea fish avoid regions where there are phosphorescent -Gorgonians or Pennatulids. It is not by any means certain that fish -avoid sunken nets on account of their phosphorescence. Most fish -possess, as is well known, a very acute sense of smell, and it is very -probable that they avoid such nets on account of the putrid odours of -the dead animals that remain attached to them. - -Nor is there much strength in the further argument that it can hardly be -possible that there can be an amount of phosphorescent light regularly -evolved by the few deep-sea animals, having this power, sufficient to -cause any general illumination, or powerful enough to have influenced, -over the whole ocean, the evolution of complex eyes, brilliant and -complex protective colours, and complex commensal adaptations. - -We have no sound information to go upon to be able to judge of the -amount of light given off by phosphorescent animals at the bottom of the -deep sea. The faint light they show on deck after their long journey -from the depths in which they live to the surface may be extremely small -compared with the light they give in their natural home under a pressure -of 2½ tons to the square inch. The complex eyes that many deep-sea -animals exhibit were almost certainly not evolved as such, but are -simple modifications of eyes possessed by a shallow-water ancestry. - -The more recent experiments that have been made, tend to show that no -sunlight whatever penetrates to a greater depth, to take an extreme -limit, than 500 fathoms. - -Fol and Sarasin, experimenting with very sensitive bromo-gelatine -plates, found that there was no reaction after ten minutes’ exposure at -a depth of 400 metres on a sunny day in March. - -But although it is highly probable that not a glimmer of sunlight ever -penetrates to the depths of the ocean, there is in some places, -undoubtedly, a very considerable illumination due to the phosphorescence -of the inhabitants of the deep waters. - -All the Alcyonarians are, according to Moseley, brilliantly -phosphorescent when brought to the surface. Many deep-sea fish possess -phosphorescent organs, and it is quite possible that many of the -deep-sea Protozoa, Tunicates, Jelly-fish, and Crustacea are in their -native haunts capable of giving out a very considerable amount of -phosphorescent light. - -If we may be allowed to compare the light of abysmal animals with that -of surface forms, we can readily imagine that some regions of the sea -may be as brightly illuminated as a European street is at night—an -illumination with many very bright centres and many dark shadows, but -quite sufficient for a vertebrate eye to distinguish readily and at a -considerable distance both form and colour. - -To give an example of the extent to which the illumination due to -phosphorescent organisms may reach, I may quote a passage from the -writings of the late Sir Wyville Thomson. - -‘After leaving the Cape Verde Islands the sea was a perfect blaze of -phosphorescence. There was no moon, and although the night was perfectly -clear and the stars shone brightly, the lustre of the heavens was fairly -eclipsed by that of the sea. It was easy to read the smallest print, -sitting at the after-port in my cabin, and the bows shed on either side -rapidly widening wedges of radiance so vivid as to throw the sails and -rigging into distinct lights and shadows.’ - -A very similar sight may frequently be seen in the Banda seas, where on -calm nights the whole surface of the ocean seems to be a sheet of milky -fire. The light is not only to be seen where the crests of waves are -breaking, or the surface disturbed by the bows of the boat, but the -phosphorescence extends as far as the eye can reach in all directions. -It is impossible, of course, to say with any degree of certainty whether -phosphorescence such as this exists at the bottom of the deep sea, but -it is quite probable that it does in some places, and hence the -well-developed eyes and brilliant colours of some of the deep-sea -animals. - -On the other hand the entire absence or rudimentary condition of the -eyes of a very considerable proportion of deep-sea animals seems to -prove that the phosphorescent illumination is not universally -distributed, and that there must be some regions in which the darkness -is so absolute that it can only be compared with the darkness of the -great caves. - -It is difficult to believe that the eyes of such animals as crabs and -prawns for example would undergo degeneration if there were a glimmer of -light in their habitat, a light even so faint as that of a starlight -night in shallow water. With the faintest light the eyes would be of use -to them in seeking their prey, avoiding their enemies, and finding their -mates, and any diminution in the keenness of this sense would probably -be of considerable disadvantage to them and tend to their ultimate -extinction. - -It might be argued that the animals of the abysses of the ocean probably -feed chiefly upon the carcases of pelagic animals that have fallen from -the upper regions of the sea, and that the sense of smell is probably -the most important for them in searching for their food. That is quite -probable; but many shallow-water animals invariably seek their food by -their sense of smell without showing any traces of a weakness in their -sense of sight. It may be taken as an axiom of biology that unless a -particular sense is absolutely useless to an animal or a positive -disadvantage to it, that sense will be retained. - -It may be stated then with some confidence that in the abysmal depths of -the ocean there is no trace of sunlight. It is highly improbable, on the -face of it, that any ray of light could penetrate through a stratum of -water four miles in thickness, even if the water were perfectly pure and -clear, but when we remember that the upper regions, at least, are -crowded with pelagic organisms provided with skeletons of lime and -silica, we may justly consider that it is impossible. - -The temperature of the water in the abyss is by no means constant for a -constant depth nor does it vary with the latitude. It is true that, as a -rule, the water is colder at greater depths than in shallower ones, and -that the deeper the thermometer is lowered into the sea, the lower the -mercury sinks. This is consistent with physical laws. If there is any -difference at all in the temperature of a column of water that has had -time to settle, the thermometer will always reach its highest point at -the top of the column and its lowest at the bottom, for the colder -particles being of greater specific gravity than the warmer ones will -sink, and the warmer ones will rise. - -The truth of this will be clear if we imagine a locality at the bottom -of a deep ocean with a source of great heat such as an active volcano. - -Such a source of heat would, it is true, raise the temperature of the -water in its immediate vicinity, but the particles of water thus heated -would immediately commence to rise through the superjacent layers of -colder water, and colder particles would fall to take their places. Thus -the effect of an active volcano at the bottom of the deep sea would not -be apparent at any very great distance in the same plane. In fact, -unless the bottom of the ocean was closely studded with volcanoes we -should expect to find, as indeed we do find, that the temperature of the -sea rises as the water shallows. - -If then we were to consider a great ocean as simply a huge basin of -water, we should expect to find the water at the surface warmer than the -water at the bottom. The temperature of the surface would vary -constantly with the temperature of the air above it. That is to say, it -would be warmer at the equator than in the temperate regions. The -temperature at the bottom would be the same as the lowest temperature of -the basin, that is, of the earth that supports it. - -The great oceans however cannot be regarded as simple basins of water -such as this. The temperature of the surface water varies only -approximately with the latitude. It is generally speaking hottest at the -equator and coldest at the poles, but surface currents in the -intermediate regions produce many irregularities in the surface -temperature. - -Again, although we have no means of knowing what the temperature of the -earth is at 1,000 fathoms below the surface of the ocean, it is very -probable that in the great oceans the temperature of the deepest stratum -of water is considerably lower than the true earth temperature. This is -due to currents of cold water constantly flowing from the poles towards -the equator. If these polar currents were at any time to cease, the -temperature of the lowest strata of water would rise. - -Although the polar currents cannot be actually demonstrated nor their -exact rapidity be accurately determined, the deduction from the known -facts of physical geography that they do actually exist is perfectly -sound and beyond dispute. A few considerations will, I think, make this -clear. - -If the ocean were a simple basin somewhat deeper at the equator than at -the poles, the cold water at the poles would gradually sink down the -slopes of the basin towards the latitude of the equator, and the bottom -temperature of the water would be constant all the world over. - -A few hills here and there would not affect the general statement that -for a constant depth the temperature of the lowest stratum of water -would be constant. - -But in some places ridges occur stretching across the oceans from -continent to continent, and these ridges shut off the cold water at the -bottom of the sea on the polar side from reaching the bottom of the sea -on the equator side. - -If A (fig. 1) represents a ridge stretching from continent to continent -across an ocean, and the arrow represents the direction of the current, -then the water that flows across the ridge from the polar side to the -equator side will be drawn from the layers of water lying above the -level of the ridge, and consequently none of the coldest water will ever -get across it, and from the level of the ridge to the bottom of the sea -on the equatorial side the water will have the same temperature as the -water at the level of the ridge on the polar side. - -It follows from this that in places where there are deep holes in the -bed of the ocean surrounded on all sides by considerable elevations, the -temperature of the water at the bottom will be the same as the -temperature of the water on the summit of the lowest ridges that -surround them. - -[Illustration: FIG. 1.—Diagram illustrating the passage of an ocean -current across a barrier (A).] - -This explains why it is that we find that the bottom temperature for a -given depth is frequently less in one place than it is in another, even -in places of the same parallel of latitude. One or two examples may be -taken to illustrate these points. The temperature off Rio Janeiro in -lat. 20° S. was found by the ‘Challenger’ to be 0·6° C. at a depth of -2,150 fathoms. In a similar latitude north of the equator at a depth of -2,900 fathoms the temperature was found to be 2·2° C., and at a point -near Porto Rico there is a deep hole of 4,561 fathoms with a bottom -temperature of 2·2° C. - -Again it has been shown by the American expedition that the temperature -of the water at the deepest point in the Gulf of Mexico, 2,119 fathoms, -is the same as that of the bottom of the Straits of Yucatan, 1,127 -fathoms, namely 4·1° C. And, passing to another part of the world -altogether, we find in the small but deep sea that lies between the -Philippines and Borneo that, at a depth of 2,550 fathoms, the -temperature is 10·2° C. - -These facts then show that, although at the bottom of the deep seas the -water is always very cold, the degree of coldness is by no means -constant in the same latitude for the same depth. - -We must now return to the polar currents. We have assumed above that -these currents do exist, and it is probable that by this time the reader -must have seen why they are assumed to exist. - -The water at the bottom of the ocean is exceedingly cold. Where does -this coldness come from? It is obvious that in temperate and tropical -climes it does not come from the surface. Nor is it at all probable that -it comes from the earth upon which the water rests; for, if it were so, -the temperature for water of a given depth would always be the same. We -should not find the bottom temperature of 0·4° C. at 2,900 fathoms off -Rio de la Plata and a temperature of 2·2° F. in 4,561 fathoms off Porto -Rico. - -In fact the only hypothesis that can with any show of reason be put -forward to account for the temperature of the bottom of the ocean is -that which derives its coldness from the Polar ice. - -We have at present very little evidence to enable us to judge of the -force and direction of the polar currents in the two hemispheres, but -the researches of the ‘Challenger’ prove almost conclusively that in the -Atlantic Ocean there is a very strong predominance of the Antarctic -polar current. In fact it seems very probable that the Arctic polar -current, if it exist at all, is very small and confined to the eastern -and western shores of the North Atlantic. - -It is very probable, however, that these currents at the bottom of the -ocean are extremely slow, and, as the water is never affected by tides -or storms, the general character of the deep sea is probably one of calm -repose. This is a matter of no little importance; for, in the -consideration of the characters presented by the fauna of any particular -region, it is always necessary to take into account the physical -difficulties the animals have to contend against and the modifications -of structure they present to combat these difficulties. - -Thus in a region such as that presented by the deep sea, where there are -no rapid tides, we should not expect to find such a powerful set of body -muscles in the free-swimming forms nor such a firm vertebral column as -in the animals that live in more lively water. - -Perhaps it is of the nature of an assumption to say that there are no -rapid currents and tides in the abysmal depths of the ocean, for we have -no means of demonstrating or even of calculating the rate of flow of -these waters. But it is a reasonable hypothesis and one that we may well -use until the contrary is proved. - -A fact of some importance that supports this hypothesis, as regards some -parts of the ocean at least, is presented by the sea-anemones. - -Many of the shallow-water Actinians are known to possess minute slits in -the tentacles and disc, affording a free communication between the -general body cavity or cœlenteron and the exterior. - -In many deep-sea forms the tentacles are considerably shorter and the -apertures larger than they are in shallow-water forms. It is difficult -to believe that such forms, perforated by, comparatively speaking, large -holes, could manage to live in rapidly flowing water, for if they did so -they would soon be smothered by the fine mud that composes the floor of -all the deep seas. In fact anemones of the type presented by such forms -as _Sicyonis crassa_ are only fitted for existence in sluggish or still -water. - -[Illustration: FIG. 2.—_Sicyonis crassa._ M, mouth; S, ciliated groove; -T, tentacles. Each tentacle is perforated by a single large aperture. -(After Hertwig.)] - -Another character that must be taken into consideration is that -presented by the floor of the great oceans. The floor of the ocean, if -it were laid bare, would probably present a vast undulating plain of -fine mud. Not a rock, not even a stone would be visible for miles. - -The mud varies in different parts of the globe according to the depth, -the proximity to land, the presence of neighbouring volcanoes or the -mouths of great rivers. - -The Globigerina ooze is perhaps the best known of all the different -deep-sea deposits. It was discovered and first described by the officers -of the American Coast Survey in 1853. It is found in great abundance in -the Atlantic Ocean in regions shallower than 2,200 fathoms. Deeper than -this, it gradually merges into the ‘Red mud.’ It is mainly composed of -the shells of Foraminifera, and of these the different species of -Globigerina are the most abundant. It is probably formed partly by the -shells of the dead Foraminifera that actually live on the bottom of the -ocean and partly by the shells of those that live near the surface or in -intermediate depths and fall to the bottom when their lives are done. - -So abundant are the shells of these Protozoa that nearly 95 per cent. of -the Globigerina ooze is composed of carbonate of lime. The remaining -five per cent. is composed of sulphate and phosphate of lime, carbonate -of ammonia, the oxides of iron and manganese, and argillaceous matters. -The oxides of iron and manganese are probably of meteoric origin; the -argillaceous matter may be due to the trituration of lumps of pumice -stone and to the deposits caused by dust storms. - -[Illustration: FIG. 3.—Globigerina ooze. (After Agassiz.)] - -Globigerina ooze may be found on the floor of the ocean at depths -ranging from 500 to 2,800 fathoms of water in equatorial and temperate -latitudes. The reason that it is not found in Arctic seas may be that -the cold surface waters of these regions do not bear such an abundant -fauna of Foraminifera. This is supported by the fact that it extends ten -degrees further north than south in the Atlantic, the warm water of the -Gulf Stream bearing a richer fauna than the waters of a corresponding -degree of latitude in the Southern Sea. - -The Pteropod ooze has only twenty-five per cent. of carbonate of lime. -It contains numerous shells of various Pteropods, Heteropods, and -Foraminifera, but nearly fifty per cent. of its substance is composed of -the siliceous skeletons of Radiolaria and the frustules of diatoms. - -According to Murray it is found in tropical and subtropical seas at -depths of less than 1,500 fathoms. - -The Radiolarian ooze is found only in the deepest waters of the Central -and Western Pacific Ocean. In some of the typical examples, not a trace -of carbonate of lime was to be found, but in somewhat shallower waters a -few small fragments occurred. - -A Diatom ooze, mainly composed of the skeletons of diatoms, has also -been found in deep water near the Antarctic Circle, but it has not -apparently a very wide range. - -Of all the deep-sea deposits, however, the so-called ‘Red mud’ has by -far the widest distribution. It is supposed to extend over one-third of -the earth’s surface. It is essentially a deep-sea deposit, and one that -is found in its typical condition at some considerable distance from -continental land. Like the Globigerina ooze it is never found in -enclosed seas. To the touch it is plastic and greasy when fresh, but it -soon hardens into solid masses. When examined with the microscope it is -seen to be composed of extremely minute fragments rarely exceeding 0·05 -mm. in diameter. It contains a large amount of free silica that is -probably formed by the destruction of numerous siliceous skeletons, and -a small proportion of silicate of alumina. It usually contains the -remains of diatoms, radiolaria, and sponge spicules, and occasionally -lumps of pumice stone, meteoric nodules, and, in colder regions, stones -and other materials dropped by passing icebergs. - -In the great oceans, then, we find in the deepest places red mud, or, -where there is an abundant Radiolarian surface fauna, Radiolarian ooze; -in water that is not deeper than about 2,000 fathoms, we find the -Globigerina ooze; in shallower waters and in some localities only -Pteropod ooze. - -It must not be supposed that sharp limits can anywhere be drawn between -these different kinds of deposits, for they pass gradually into one -another and present many intermediate forms. - -It is probable that the sea water by virtue of the free carbonic acid it -contains in solution is able to exert a solvent action upon the calcium -carbonate shells of animals as they sink to the bottom, and during the -long and very slow journey from the surface to the bottom of the deepest -seas these shells are completely dissolved. - -The first to be dissolved would be the thin delicate shells of the -Pteropods and Heteropods, for besides the fact that they present a wider -surface to the solvent action of the water they are probably influenced -more by tide and currents, sink more slowly and erratically, and thus -have a longer journey to perform. - -Then the smaller but more solid and compact shells of the Foraminifera -are dissolved, and lastly, in the deepest water only the siliceous -skeletons of the radiolaria and diatoms are able to reach their last -resting place at the bottom of the ocean. - -These four oozes then are characteristic of the floor of the deep -oceans. In the proximity of land and in inland seas where deep water -occurs, other muds are found differing from one another in accordance -with the character of the coasts in their vicinity. It is not necessary -to give a detailed account of them, but a few remarks on some of the -more pronounced forms may not be without interest. - -The blue mud contains eighty per cent. of a mixture of quartz, mica, -felspar, hornblende, and other minerals, mixed with a considerable -quantity of decomposing animal and vegetable substance, the calcareous -remains of foraminifera, mollusca, worms, echinoderms, alcyonaria and -corals, and the siliceous skeletons of radiolaria and diatoms. - -The green mud is characterised by a large percentage of glauconite. - -The red muds characteristic of the Brazilian coast contain a large -amount of ochreous matter brought into the sea by the great rivers. - -In the neighbourhood of active volcanoes there is a characteristic -volcanic mud, and in the coral seas the deep-sea deposits contain a -large percentage of the calcareous remains of dead corals. - -One more character of the deep-sea region must be referred to before we -pass on, and that is the absence of vegetable life. It has not been -determined yet with any degree of accuracy where we are to place the -limit of vegetable life, but it seems probable that below a hundred -fathoms no organisms, excepting a few parasitic fungi, are to be found -that can be included in the vegetable kingdom. While then the researches -of recent times have proved beyond a doubt that there is no depth of the -ocean that can be called azoic, they have but confirmed the perfectly -just beliefs of the older naturalists that there is a limit where -vegetable life becomes extinct. It is not difficult to see the reason -for this. All plants, except a few parasites and saprophytes, are -dependent upon the influence of direct sunlight, and as it has been -shown above that the sunlight cannot penetrate more than a few hundred -fathoms of sea water, it is impossible for plants to live below that -depth. - -The absence of vegetable life is an important point in the consideration -of the abysmal fauna, for it is in consequence necessary to bear in mind -that the food of deep-sea animals must be derived from the surface. It -is possible that deep-sea fish, in some cases, feed upon one another and -upon deep-sea crustacea, that deep-sea crustacea feed upon deep-sea -worms, that deep-sea echinoderms feed upon deep-sea foraminifera, and so -on through all the different combinations; but the fauna would soon -become exhausted if it had no other source of food supply. This other -source of food supply is derived from the bodies of pelagic organisms -that fall from the upper waters of the ocean, and is composed of -protozoa, floating tunicates, crustacea, fish, and other animals, -together with diatoms and fragments of sea-weed. - - - - - CHAPTER III - THE RELATIONS OF THE ABYSMAL ZONE AND THE ORIGIN OF ITS FAUNA - - -In the study of the geographical distribution of terrestrial animals one -of the great difficulties met with is the impossibility of defining -exactly the limits of the regions into which we divide the surface of -the earth. In a general way we recognise that there is an Australian -region, an Ethiopian region, &c.; but, when we come to discuss the exact -position of the frontier lines that separate these regions from their -neighbours, we find all kinds of difficulties to overcome and -inconsistencies to meet. - -For the sake of convenience it is useful to adopt certain arbitrary -limits for these regions, notwithstanding these difficulties and -inconsistencies, but we must recognise the fact that nature recognises -no such limits, that every region overlaps its neighbours to a greater -or less extent, and that there are many debateable grounds in the world -where the fauna characteristic of one region is mixed with that -characteristic of another. - -But this difficulty in defining the exact limits of the terrestrial -faunistic regions is even more pronounced in the case of the regions and -zones of the marine fauna. - -On the dry land we find mountain ranges, forests, deserts, and other -barriers, that to a very considerable extent prevent the mixing of one -fauna with another, but in the sea there are no barriers of anything -like the same importance, but one fauna gradually merges into the -neighbouring fauna according to the temperature, the pressure, the -amount of light, the salinity of the water or the food supply. This then -is one of the difficulties met with in the study of the geographical -distribution of the marine fauna. - -But there is another that leads to almost greater complications. In -considering terrestrial life it is customary to refer only to regions of -geographical, or perhaps it would be more correct to call it—superficial -distribution. It would be quite possible, however, to subdivide the -geographical areas into zones of elevation above the sea-level, not very -clearly marked off from one another, it is true, but nevertheless each -showing a number of characteristic features. This idea is expressed, for -example, when we speak of the Alpine fauna, the Himalayan fauna, or the -fauna of the great Andes. - -In the study of the marine fauna and flora we must notice, it is the -depth of the water, or in other words the depression of the habitats -below the sea-level, that forms the most important consideration. -Geographical sub-regions may be recognised and defined with a certain -amount of accuracy, especially in the case of the fauna of the shallow -waters, but by far the most important changes in the general characters -of the fauna are found when we pass from one ‘zone’ of depression to -another. Thus in describing any particular marine fauna we should -mention first of all its zone or sub-zone of depression and then its -geographical region and sub-region. For example, we may speak of the -fauna of the pelagic zone of the British sub-region of the European -region, or the fauna of the abysmal zone of the Northern sub-region of -the Atlantic region. - -We can recognise three primary zones of the marine fauna which we may -call the ‘Pelagic,’ the ‘Neritic,’ and the ‘Abysmal’ zones. - -The Pelagic zone includes the superficial waters of all seas extending -from the surface to a depth which cannot at present be very accurately -determined, but is probably the same as the limit of the influence of -direct sunlight. - -The animals of this zone are frequently characterised by a general -transparency of their tissues, a white or sea water (i.e. blue or green) -colour, an organisation capable of prolonged swimming or floating -movement, and by giving birth to floating eggs which hatch out -transparent larvæ or embryos. - -The pelagic zone may be divided into several geographical regions and -sub-regions, which it would be beyond the scope of this book to -enumerate here, but there is one that calls for a few brief remarks. In -many parts of the ocean there may be found vast areas of floating -sea-weed, which carry with them a population of crustacea and other -animals peculiarly their own. This ‘sargasso’ fauna presents so many -characteristics and so many features different from that of the ordinary -pelagic fauna, that the tracts of sea bearing this weed must be -considered to rank as a special region of the pelagic zone, which may be -called the Sargasso region. - -The zone of shallow water for which we shall adopt Professor Haeckel’s -term—the Neritic zone—embraces all parts of the seas of less depth than -500 fathoms, including the inland seas, the shores of great continents -and islands, and the shallow banks in the great oceans. It does not -include the superficial waters—which belong to the pelagic zone—but -extends only from the actual bottom to a distance of a few fathoms above -it. The fauna of this zone is extremely varied, consisting of animals -that swim, crawl, or are permanently fixed to the bottom, animals of -almost every variety of colour and marking, and of every size and shape. - -The exact limits of the Neritic sub-zones are not easy to define. The -distinguished naturalist Forbes, to whom the abysmal zone was unknown, -divided the seas from 0–50 fathoms in depth into three zones—the -littoral zone lying between tide-marks, the laminarian zone extending -from 0–15 fathoms, and the coralline zone from 15–50 fathoms. - -The first of these will stand as a sub-zone, the animals that are able -to withstand exposure to the sun and air either in pools or upon the -rocks and sand even for a few minutes frequently possessing features -that distinguish them from those dwelling beyond low-water mark, just as -those more active creatures that migrate backwards and forwards with the -ebb and flow of every tide differ from the dwellers in the open sea. -There is, it is true, at every low tide, a migration of part of the -fauna of this sub-zone into the next, but still it is sufficiently well -defined to be allowed to remain in our category. - -The second sub-zone is not so easy to define. The terms ‘laminarian’ and -‘coralline’ used by Forbes are only applicable to certain geographical -regions and must be abandoned for general use. - -We can only recognise one sub-zone between the littoral sub-zone and the -abysmal zone, for notwithstanding the important varieties it exhibits in -the nature of the bottom, whether it be rocky, sandy, or weedy, the -amount of light, the temperature of the water, and the rapidity of the -currents, it is not possible at present to point to any general -characters of the fauna of its different parts to justify us in -subdividing it. - -The name that may be given to this second sub-zone of the neritic zone -is the Katantic—the sub-zone of the slopes. - -The last well-marked zone is the abysmal, extending from the 500–fathom -line to the greatest depths of the ocean, one of enormous superficial -area, one that it is most difficult to investigate, and one about which -we know but little. - -In the present state of our knowledge we cannot divide it into any -well-marked sub-zones nor even into geographical regions or sub-regions. -It is not divided into sections by any important geographical barriers, -and the general characters presented by its fauna are practically the -same all the world over. - -Professor A. Agassiz has pointed out in his ‘Challenger’ monograph that -the deep-sea echinoids of the Atlantic Ocean differ from those living in -corresponding depths in the Pacific Ocean, but it is doubtful whether -any such well-marked differences can be observed in other groups of -animals. If, in the course of time, increased knowledge of deep-sea -animals emphasises the difference between the abysmal fauna of the -Pacific and that of the Atlantic, then we can divide this zone into two -geographical regions; but at present it seems more correct to consider -the abysmal zone as one that is indivisible either bathymetrically or -geographically. - -Before passing on to the consideration of the general characters of the -abysmal fauna, there are still one or two points that must be just -briefly referred to. - -It is the function of every true naturalist to consider animals from -every possible point of view. Not only must he regard them as members of -a certain species belonging to a genus, a family, an order, and so on, -presenting certain peculiarities of structure and development; not only -must he regard them as inhabitants of a certain locality or zone of -depth, but he must also pay attention to their habits and mode of life. - -Now amongst marine animals we can recognise three principal modes of -life. Some animals simply float or drift about with the currents of the -sea and are unable to determine for themselves, excepting, perhaps, -within very small limits, the direction in which they travel. Such are -the countless forms of protozoa, the jelly-fishes and medusæ, numerous -pelagic worms and crustacea, the pyrosomas and salps, and many other -forms well known to those who are in the habit of using the tow-net. -This portion of the fauna has recently been called the Plankton. - -Then there are the animals that are capable of very considerable -swimming movements, animals that are able to stem the tide and migrate -at will from one part of the sea to another, such as the cetacea, most -fishes, and perhaps also many cephalopods. This portion of the fauna has -been called the Nekton. - -And lastly we have those animals that remain perfectly fixed to the -bottom or are capable only of creeping or crawling over the rocks and -sand, such as the sponges, hydroids, sedentary tunicates, gasteropods, -most lamellibranchs, and many crustacea. This portion of the fauna has -been called the Benthos. - -Although it will not be necessary to use these terms very frequently in -this little book, it may be advisable for the reader to bear in mind -that in any exhaustive treatise on the marine fauna such terms would be -employed, and that in the chapters dealing with the fauna of the abysmal -zone we should find accounts of the ‘bathybial plankton,’ the ‘bathybial -nekton,’ and the ‘bathybial benthos.’ - -Lastly we must consider quite briefly the views that have been held -concerning the origin of the abysmal fauna. - -As soon as it became clear to naturalists that there is no part of the -ocean, however deep it may be, that deserves the name ‘azoic,’ but that -almost every part has a fauna of greater or less density, the problem of -the origin of this fauna presented itself. - -Whence came the curious creatures that live mostly in total darkness and -can sustain without injury to their delicate and complicated -organisation the enormous pressure of the great depths? Are they the -remnants of the fauna of shallow prehistoric seas that have reached -their present position by the gradual sinking of the ocean basins? Or, -are we to look upon the abysmal region as the nursery of the marine -fauna, the place whence the population of the shallow waters was -derived? Neither of these answers is supported by the facts with which -we are now well acquainted. The fauna of the abysmal region does not -show a close resemblance to that of any of the past epochs as revealed -to us by geology, nor are we justified in assuming without much stronger -evidence than we now possess, that the oceans have undergone any such -great depression as this first theory presupposes. - -Nor can we consider for a moment that the abyss was the original source -of the shallow-water fauna; for not only do we find but few types that -can be considered to be, in any sense of the word, ancestral in -character; but on the contrary most of the animals of the deep sea seem -to be specially modified types of shallow-water forms. The most probable -explanation of the origin of the deep-sea fauna is the one that was put -forward by Moseley and has been since supported by almost every -authority on the subject, namely, that the fauna of the deep sea has -been derived from successive immigrations of the animals from the -shallow water. - -This view is supported by the fact that the deep-sea fauna is much -richer in the neighbourhood of land than it is in regions more remote -from it. Many examples could be given to illustrate this point. The -extraordinary richness of the deep-sea fauna on the western slopes of -the floor of the Atlantic has been frequently commented on by the -naturalists connected with the expeditions of the American vessels, the -‘Blake,’ the ‘Fish Hawk,’ and the ‘Albatross.’ Moseley called attention -several years ago to a few localities in the neighbourhood of the land -especially rich in deep-sea forms in comparatively shallow waters, such -as one near the island of Sombrero in the Danish West Indies, where -within sight of the lighthouse a haul of the dredge in 450 fathoms -brought up a rich fauna of blind crustacea, corals, echinoderms, -sponges, &c. Another off Kermadec in 630 fathoms brought up numerous -curious blind fishes, ascidians, cuttlefishes, crustacea, _Pentacrinus_, -and large vitreous sponges, and there are similar localities lying -between Aru and Ke and between the Nanusa archipelago and the Talaut -islands. The deep water off the Norwegian, Scotch, Irish, and Portuguese -coasts also seems to be particularly rich in various forms of animal -life. The same is probably true of the deep sea of many other regions in -the neighbourhood of land, and, although it cannot be taken to be a rule -without exceptions—the abysmal fauna off the western coasts of the -Panama region being, according to the recent researches of Alexander -Agassiz in the ‘Albatross,’ particularly poor—yet we can assert as a -statement of very general application that the further removed from -continental land, the poorer is the abysmal fauna. - -Another argument that has been brought forward by Moseley in support of -his view is that there is a certain relationship between the deep-sea -fauna of any particular region and the shallow-water fauna of the -nearest coasts. This is a point that is not easy to illustrate by -examples, but as Moseley’s argument has not, so far as I am aware, been -disputed by any of the naturalists who have followed him in this line of -work, and the recent results of the ‘Albatross’ in comparing the -deep-sea fauna of the eastern and western sides of the isthmus of Panama -seem if anything to support it, we can take it as a point in favour of -his view of the origin of the abysmal fauna. - -It is impossible to say at present at what time in the world’s history -these migrations commenced, but, as Agassiz points out, none of the -palæozoic forms are found in the deep sea, and this seems to indicate -that the fauna did not commence its existence earlier than the -cretaceous period. - -It is quite possible, however, that part of the fauna of the deep sea -has been derived directly from the pelagic zone. The occurrence of -bathybial Radiolaria, Foraminifera and Siphonophora, and among fishes -genera and species of the pelagic families Sternoptychidæ and Scopelidæ, -suggest that this zone may have contributed very largely to the fauna of -the abyss. - -Much of course still remains to be done before we can consider any of -these interesting problems connected with the deep-sea fauna to be -definitely solved. All we can do at present is to speculate upon the -direction in which the facts at our disposal seem to point, and by -following up one clue after another hope that we may eventually arrive -at the truth. The task may be a difficult one, but it will reward our -efforts. If truth is hard to find when it lies at the bottom of a well, -how much more inaccessible must it be when it lies hidden in the -darkness of the sea’s abyss! - - - - - CHAPTER IV - THE CHARACTERS OF THE DEEP-SEA FAUNA - - -The general characters presented by animals living in deep water may be -considered under several headings. The most important are those that are -directly or indirectly related to the fact that the animals live either -in total darkness or in the faint and probably intermittent light -emitted by phosphorescent animals; namely, the colour of the skin and -the peculiarities of the eyes. - -The colours of the skin of the deep-sea animals vary to a very -remarkable extent in the different groups. It cannot be said that there -is any one colour at all predominant, and it is only in certain classes -that black, white, or dull-coloured animals are more numerous than -others. The colours are however usually very evenly distributed, and we -find but few examples of animals with spots, stripes, or other -pronounced markings. - -The majority of the fish are dark brown or black, but many other colours -are represented. Thus _Ipnops Murrayi_, a typical deep-sea fish, is -yellowish brown with colourless fins, and it exhibits a further -character not uncommon in these abysmal forms, namely black buccal and -branchial cavities. _Typhlonus nasus_, again, is said to be of a light -brownish colour, with black fins. Many other examples could be given to -show the prevalence in these regions of these black, dull, and pale -uniform colours. But there are many exceptional cases. _Neoscopelus -macrolepidotus_, for example—a form that according to Günther -undoubtedly belongs to the bathybial region—is distinguished by its -brilliant colours. It is bright red mixed with azure blue, the whole -relieved by silver spots with circles of black on the abdomen. - -_Prorogadus nudus_ is of a pale rose colour, with the under and lateral -sides of the head bluish black. - -_Rhodichthys regina_, found in 1,280 fathoms of water, is uniformly -bright red in colour. - -A. Agassiz says in his reports on the dredging operations on the west -coast of America: ‘The coloration of the deep-sea fishes is -comparatively monotonous. The tints are all a light violet base, tending -more or less to brownish or brownish yellow, or even to a greenish tint, -especially among the Macruridæ. Some of the Liparidæ were of a dark -violet, and one species was characterised by a brilliant blue band. The -Ophidiidæ, _Nemichthys_, and the like, are usually of an ashy violet -tint, while in _Ipnops_ and _Bathypterois_ the tints were of a decidedly -yellowish brown.’ - -That the deep-sea fish are usually devoid of any pronounced spots, -stripes, and other markings, is now well recognised. It may not be -altogether out of place, however, to refer briefly to a few exceptions. - -The black circles on the abdomen of _Neoscopelus macrolepidotus_ have -already been referred to. - -_Halosaurus johnsonianus_, has a black spot on the tail. - -_Aulostoma longipes_ has three pairs of large black spots on the ventral -side, but the specimen taken in 1,163 metres of water by the ‘Talisman’ -was probably a young one. - -It is very probable that in all the exceptional cases, when fish taken -in deep-sea water have exhibited such spots and markings, they are -examples either of fish that have quite recently adopted an abysmal -habitat or of young specimens exhibiting ancestral inherited characters. - -In referring to a specimen of _Raja circularis_, taken by the ‘Triton’ -in 516 fathoms, Günther says: ‘It is notable that the spot on each side -of the back which in littoral specimens is variegated with yellow is -much smaller in the deep-sea specimen and uniformly black without -yellow.’ - -It seems to be then a very general rule among fishes that as they -migrate into deeper water the spots and stripes, so conspicuous among -many forms living on the surface and in shallow water, disappear, and -the coloration of the body becomes more evenly distributed and uniform. - -Among the Mollusca, the deep-sea Cephalopods seem to be usually violet, -but an _Opisthoteuthis Agassizii_ caught by the ‘Blake’ is stated to be -of a dark chocolate colour, a _Nectoteuthis Pourtalesii_ reddish-brown, -and a _Mastigoteuthis_ orange brown, while of the specimens brought home -by the ‘Challenger,’ _Cirroteuthis magna_ was said to be ‘rose’ when -captured, and the spirit specimens of _Cirroteuthis pacifica_ and -_Bathyteuthis abyssicola_ were purplish madder and purplish brown -respectively. - -The shells of the Gasteropods and Lamellibranchs living in the abyss are -frequently so thin as to be almost transparent, and are, with very few -exceptions, white or pale straw coloured. The colour of the only -specimen of nudibranchiate Mollusca that has been found in the abysmal -zone, namely, _Bathydoris abyssorum_, is described by Mr. Murray as -follows: ‘The body of the living animal was gelatinous and transparent, -the tentacles brown, the gills and protruding external generative organ -orange, the foot dark purple.’ - -Among the Crustacea various shades of red are the prevailing colours. -‘The deep-sea types, like _Gnathophausia_, _Notostomus_, and -_Glyphocrangon_,’ says Agassiz, ‘are of a brilliant scarlet; in some -types, as in the Munidæ and Willemoesiæ, the coloration tends to pinkish -or yellowish pink, while in _Nephrops_ and _Heterocarpus_ the scarlet -passes more into greenish tints and patches.’[1] But perhaps the most -remarkable point in the colour of the crustacea is that which -immediately follows the paragraph I have just quoted. ‘The large eggs of -some of the deep-sea genera are of a brilliant light blue, and in one -genus of Macrura we found a dark metallic blue patch on the dorsal part -of the carapace in marked contrast to the brilliant crimson of the rest -of the body.’ - -Footnote 1: - - In the recent researches of the ‘Investigator’ a few crustacea of - rather exceptional colour were found. Whilst the great majority of - them are described to be pink or red in colour when alive, - _Gnathophausia bengalensis_ is deep purple lake, _Haliporus neptunus_ - lurid orange, and _Aristaeus coruscans_ bright orange. - -The occurrence of this blue colour in Crustaceans of the deep sea is -very remarkable, for blue is a colour, as Moseley pointed out many years -ago, that is rarely met with in the fauna of the abyss, and it is -certainly very exceptional in the crustacea of that zone. - -Among the deep-sea Echinoderma we find a wonderful variety of -coloration. Moseley says that many deep-sea Holothurians, for example, -are deep purple, and Agassiz reports that in one species the colour was -of a delicate green tinge. ‘We obtained,’ he adds, ‘a white _Cucumaria_ -and some species of _Benthodytes_ of the same colour,’ while others vary -from transparent milky white to yellow and light yellowish brown and -even pinkish colours. The Crinoids are described by the authorities to -be white, purple, yellow and brownish-chestnut, and of the other groups -of the echinoderms we read that the star-fishes are, as a rule, of -duller colours than the crustacea, but all more or less pink or red. -‘The Hymenasteridæ, on the contrary, vary from light bluish violet to -deep reddish chestnut colours.’ The brittle stars are red and orange or -dullish grey, while the urchins may be deep violet, claret coloured, -brownish, or of a delicate pink. - -It is impossible to account for this extraordinary variety of colour in -the deep-sea echinoderms. It is hardly probable that it can be -protective or warning in function, and it is difficult to suppose that -it is due to any peculiar excretory process. Whether it is due in any -way to the influence of the environment, or, like the colour of autumn -leaves, to the chemical degeneration of colours that in the -shallow-water ancestry were functional, are problems that must be left -for the future to decide. - -The colour of the deep-sea Cœlenterates has unfortunately not been -recorded in all cases, but still the few observations that we have show -that in this group, as in the last, almost every tint and shade are -represented. - -The colouring of the deep-sea jelly-fishes is said to be usually deep -violet or yellowish red. However ‘a species of _Stomobrachium_,’ says -Agassiz, ‘is remarkable for its light carmine colour, a tint hitherto -not observed among Acalephs.’ - -Moseley records most minutely the colour of some of the deep-sea -anemones and corals, and calls attention to the very general presence of -madder brown in the soft parts. Agassiz says: ‘Among deep-sea Actiniæ, a -species of a new _Cereanthus_ was of a dark brick-red, while other -actinians allied to _Bunodes_ were of a deep violet. Actinauge-like -forms with tentacles of a pinkish-violet tinge frequently have the -column of a yellow shade. The Zoanthidæ were greyish-green.’ And again, -in his narrative of the voyage of the ‘Blake,’ he records that ‘some of -the deep-sea corals are scarlet, deep flesh-coloured, pinkish orange, -and of other colours,’ and in referring to the Gorgonian _Iridogorgia_ -he says: ‘The species are remarkable for their elegance of form and for -the brilliant lustre and iridescent colours of the axis, in some of a -bright emerald green, in others like burnished gold or mother-of-pearl.’ - -The fauna of the deep sea then, taken as a whole, is not characterised -by the predominance of any one colour. The shades of red occur rather -more frequently than they do in the fauna of any other zone or region, -but whether this is in any way connected with the fact that red is the -complementary colour to that of the phosphorescent light, in which many -of these animals live, it is at present difficult to say; it is possible -that, when we have further information concerning the colours of the -animals living in the deeper parts of the Neritic zone, another -explanation may be forthcoming. - -Moseley points out that there are no blue animals known to live in deep -water, and it might be added that green is extremely rare as a colouring -matter in abysmal animals, although the phosphorescent light given out -by some of the echinoderms is green. - -Blue, as a colouring matter of marine animals, living on the surface or -in shallow water, is not uncommonly met with, distributed in the form of -bands or stripes, but green is extremely common in fishes, crustacea and -cœlenterates, and it is a point of very considerable importance that in -this respect there is a very great difference between the deep-sea and -the shallow-sea faunas. - -If a considerable collection of living abysmal forms could be placed -upon one table and a similar collection of shallow-water forms upon -another, I believe that the first general impression upon the mind of -one who saw them both for the first time would be the presence of green -colours in the last-named collection, and the absence of it in the -other. - -The eyes of the animals that live in deep-sea water undergo curious -modifications. If the fauna of the abysmal region were confined to -conditions of absolute darkness, we should expect to find either a total -absence of eyes or mere rudiments of them only in those forms that have -recently migrated from the shallow water. This is the case with the -fauna of the great caves. There is probably total darkness in these -underground lakes and streams, and there is only the remotest -possibility of the animals living in them ever seeing, even temporarily, -a ray of sunlight or even a glimmer of phosphorescence during the whole -of their life-time. We find then that the cave fauna is totally blind. - -The conditions in the deep sea are not quite the same. In some regions -there is probably a very considerable illumination by phosphorescent -light, and it is quite possible that many of the characteristic deep-sea -forms may occasionally wander into shallower regions where faint rays of -sunlight penetrate, or even that the young stages of some species may be -passed at or near the surface of the sea. Taking these points into -consideration, then, it is not surprising to find that, in the deep -seas, there are very few animals, belonging to families usually provided -with eyes, that are quite blind. - -In the majority of cases we find that the eyes are either very large or -very small. Only in a small minority of cases do we find that the eyes -are recorded to be moderate in size. The relation between the large-eyed -forms and the small-eyed forms is not the same in all the regions of -deep seas. In depths of 300 to 600 fathoms the majority are large-eyed -forms. This is as we should expect, for it is more than probable that -many of these forms occasionally wander into shallower waters where -there is a certain amount of sunlight. - -In depths of over 1,000 fathoms, the small-eyed and blind forms are in a -majority, although many large-eyed forms are to be found. - -Among fishes, for example, we find the species of _Haloporphyrus_ found -in depths of 300–600 fathoms with large eyes; and so with _Dicrolene_, -_Cyttus abbreviatus_, and many other forms that are known to live in -water of less depth than 700 fathoms; while on the other hand in -_Melanocetus Murrayi_, _Ipnops Murrayi_, many deep-sea eels and other -fish that are truly abysmal and live chiefly in depths of over 1,000 -fathoms, the eyes are either very small or absent. - -Some interesting examples may be found in the species of widely -distributed genera to illustrate these points. Thus in _Neobythites -grandis_, from 1,875 fathoms, the eye is small, only one-eleventh the -length of the head, but in _Neobythites macrops_, _N. ocellatus_, and -_N. gillii_ from shallower water it is much larger. - - N. grandis 1,785 fms. Eye 1⁄11th length of the head - N. macrops 375 fms. Eye 2⁄9 length of the head - N. ocellatus 350 fms. Eye ¼ length of the head - N. gillii 111 fms. Eye 1⁄(3⅔) length of the head - -Similarly in the species of the widely distributed deep-sea genus -_Macrurus_: the species _M. parallelus_, _M. japonicus_, _M. fasciatus_, -&c., usually living in water less than 1,000 fathoms deep, have large -and in some cases very large (_M. fasciatus_) eyes, but _Macrurus -filicauda_, _M. fernandezianus_, _M. liocephalus_, _M. Murrayi_, _M. -armatus_ have small eyes. - -Some deep-sea fish have their eyes reduced to a mere rudiment; such as -_Ceratias uranoscopus_, _C. carunculatus_, _Melanocetus Murrayi_, -_Typhlonus nasus_, and _Aphyonus gelatinosus_, but not even a rudiment -of an eye is to be found in _Ipnops Murrayi_. - -But the fish of the greatest depths are by no means always characterised -by small eyes. _Malacosteus_, a typical deep-sea form, has very large -eyes, and so have _Bathylagus_, living in the enormous depth of 3,000 -fathoms, and _Bathytroctes_, in 1,090 and 2,150 fathoms. - -The result of recent deep-sea work, then, has been to show that as we -proceed from shallow shore water to depths of 500 to 900 fathoms the -eyes of the fish become larger, but in greater depths than 1,000 fathoms -the eyes of some fish become considerably reduced, but those of others -become still more enlarged. In the greatest depths of the ocean in fact -it seems very probable that nearly all the fish are characterised by -either very large eyes or very small ones. - -We cannot expect to learn very much at present from the study of the -eyes of deep-sea mollusca. The Cephalopods form the only class of this -Phylum whose genera invariably possess large and well-developed eyes, -and there does not seem to be any very marked increase or decrease in -the size of the eyes of the few deep-sea cuttlefish that are known to -us. - -The eye of _Nautilus_ is certainly remarkably interesting, but as this -genus is the only representative of its order, and is known at times to -float upon the surface of the ocean, it would certainly be erroneous to -attribute the peculiarity of the structure of its eye to its ‘temporary’ -deep-sea habits. We are still ignorant of the usual habitat of the -remarkable genus _Spirula_, notwithstanding the fact that many of the -tropical beaches are very largely composed of its empty shells. Whether -it is a deep-sea dweller or not, we know nothing at present of the -character of its eye, so that it can throw no light upon the problems we -are now discussing. - -Among the deep-sea gasteropods we find the same irregularity in the -possession of eyes that we have just described among fishes. Thus a -species of _Pleurotoma_, dredged by the ‘Porcupine,’ in 2,090 fathoms, -has a pair of well-developed eyes on short footstalks, but _Pleurotoma -nivalis_, obtained by the ‘Talisman,’ is blind. Again a species of -_Fusus_, obtained by the ‘Porcupine,’ in 1,207 fathoms, is provided with -well-developed eyes, but _Fusus abyssorum_, obtained by the ‘Talisman,’ -is blind. Among the Lamellibranchs there are very few genera that -possess well-marked eyes. The genus _Pecten_ is one of those that in -shallow waters possess numerous highly complicated visual organs -situated on the edge of the mantle. In the deep-sea species, _Pecten -fragilis_, these eyes are wanting, but we have not sufficient evidence -at present to enable us to assert that all the deep-sea species of this -genus are blind. - -Among the Crustacea there is a very general tendency to lose the eyes at -a depth of a few hundred fathoms of water. - -In _Ethusa granulata_, for example, the eyes disappear at 500 fathoms -and the eye-stalks become firmly fixed, greater in length, and take the -place of the rostrum which disappears. In some forms—such as -_Thaumastocheles zaleuca_ and _Willemoesia_—the eye-stalks themselves -have completely disappeared. - -In the deep-sea Isopoda some forms lose their eyes entirely, but -_Bathynomus giganteus_ possesses a pair of enormous eyes, each provided -with 4,000 facets. - -To illustrate the distribution of eyes in this group, we may take as an -example the genus _Serolis_. All the species of this genus are provided -with eyes except _Serolis antarctica_—a species that extends from 600 to -1,600 fathoms. - -The eyes of all the deep-sea species are relatively larger than those of -the shallow-water ones, except _Serolis gracilis_, whose eyes seem to be -disappearing. - -But these large eyes of the deep-sea species of _Serolis_ are not -capable of any greater perceptive power. In fact, the evidence of -degeneration they show, both in minute structure and in the diminution -of pigment, proves that they can be of very little use to these animals -for perception (see Figs. 4 and 5). - -This increase in size, accompanied by degeneration of structure, is just -what we should expect to find in the eyes of deep-sea animals, and it is -difficult to explain why it is that we do not find more examples of it. - -If the animals that now live in the depths of the sea are descended from -the shallow-water forms of bygone epochs, they must have passed through -many different habitats with diminished light until they reached their -present dark abode in the abyss. - -[Illustration: FIG. 4.—Semi-diagrammatic section through the eye of -_Serolis schythei_, a shallow-water species (4–70 fathoms). C, lens; V, -crystalline cone; R, rhabdom; N, nerve. (After Beddard.)] - -[Illustration: FIG. 5.—Diagrammatic section of the eye of _Serolis -bromleyana_, a deep-sea species (400–1,975 fathoms), showing the -degenerate character of the eye. The corneal facets C, and the -crystalline cones V, are the only structures that can be recognised. -(After Beddard.)] - -In every new region they came to, the forms with larger and better eyes -would be at an advantage in the fainter light, and would be more likely -to survive and transmit their favourable variation in this respect to -their offspring than their less fortunate neighbours. Thus down to the -depth of the limit of sunlight we should expect to find, as we do find -in fishes, large-eyed species. - -Beyond the limit of direct sunlight the eyes would be of very little use -to them, the pigment would disappear and the tissues become degenerate. -This is precisely what has occurred in the genus _Serolis_. - -The disappearance of the sense of sight in the animals of the deep sea -is sometimes accompanied by an enormous development of tactile organs. - -Thus, among fishes we find _Bathypterois_, a form that possesses -extremely small eyes, provided with enormously long pectoral fin rays -that most probably possess the functions of organs of touch. - -Among the Crustacea we find the blind form, _Galathodes Antonii_, with -an extraordinary development in length of the antennæ, and -_Nematocarcinus_, with enormously long antennæ and legs. - -The subject of the power of emitting phosphorescent light possessed by -some deep-sea animals is much more difficult to deal with. - -The presence of distinct organs in many of the deep-sea fish that can -only be reasonably interpreted as phosphorescent organs, the presence of -well-developed and evidently functional eyes in many deep-sea animals, -and many other considerations render it very highly probable that some, -if not many, forms emit a phosphorescent light. - -The power and constancy of the light emitted, however, must for the -present remain a matter of conjecture. We cannot judge at all of the -amount of light given out by an animal in deep water by its appearance -when thrown out of a dredge upon the deck. Whether the phosphorescent -light given out by an Alcyonarian or a Crustacean is more or less at a -temperature of 40° Fahr. and a pressure of one ton per square inch than -it is at 60° Fahr. and the ordinary barometric pressure of the -sea-level, is a question that has not yet been brought to an -experimental test. - -Whatever the answer to this question may be, the fact remains that a -greater percentage of animals from the deep sea exhibit some sort of -phosphorescent light when brought on deck than animals that live in -shallow water. - -The curious organs possessed by some fishes that are supposed to be -organs for the emission of phosphorescent light have recently been -subjected to a minute examination by von Lendenfeld. - -It has been known for some years now, that the slime secreted by the -skin glands of certain sharks is highly phosphorescent. It is not -difficult, then, to understand how it came about that certain fish -developed complicated phosphorescent organs. - -From the phosphorescent slime secreted by a simple skin gland to the -most complicated eye-like phosphorescent organ, we have a series of -intermediate forms that are quite sufficient, even in the imperfect -state of our knowledge at the present day, to enable us to understand -the outlines of the evolution of these peculiar and interesting organs. - -We can distinguish two kinds of phosphorescent organs in the deep-sea -fish. There are the curious eye-like or ocellar organs situated usually -in one or more rows down the sides of the fish’s body, forming as it -were a series of miniature bull’s-eye lanterns to illuminate the -surrounding sea (fig. 6); and various glandular organs that may be -situated at the extremity of the barbels or in broad patches behind the -eyes or in other prominent places on the head and shoulders. - -Ocellar organs have been known for many years to occur on the sides of -the interesting pelagic fish, _Scopelus_. Most of the species of this -genus live in the open sea at moderate depths, coming to the surface -only at night, but other species are found in almost every depth down to -2,000 fathoms of water. - -[Illustration: FIG. 6.—_Opostomias micripnus_; 2,150 fathoms. (After -Günther.)] - -In _Opostomias micripnus_, a dark black fish living at a depth of over -2,000 fathoms, there are two rows of ocellar organs running down the -sides of the body from the head to the tail. In the living animal they -are said to shine with a reddish lustre. In addition to these, the -conspicuous organs, there are groups of fifty, a hundred, or even more -very much smaller organs situated on the sides and back of the fish, -each of which is lenticular in shape and consists of a number of short -polygonal tubes containing a granular substance with rounded bases -resting on the subjacent tissue. The whole organ is covered by a simple -continuation of the cuticle of the body-wall. The granular substance -contained in the tubes is most probably the seat of luminosity. - -[Illustration: FIG. 7.—Head of _Pachystomias microdon_ (after Von -Lendenfeld). A, anterior sub-orbital phosphorescent organ; B, posterior -sub-orbital phosphorescent organ.] - -As a type of the glandular organs we may take one of the sub-orbital -organs found on the head of _Pachystomias microdon_. - -In this fish there are two very conspicuous white organs immediately -below the eye. The anterior one, which lies below and in front of the -eye, is oval, with its upper margin slightly concave. In section it is -seen to be surrounded by a thin layer of black pigment, and to consist -of a reticular glandular substance in which is embedded a hammer-shaped -lens-like body. Between these two structures there is interposed a thick -layer of light reflecting spicules. - -The exact part that is played by the different components of these -curious phosphorescent organs is not yet known, but sufficient has been -said to indicate to the reader the degree of complexity that these -organs may reach in the fish of the great depths of the ocean. - -[Illustration: FIG. 8.—Section of the anterior sub-orbital -phosphorescent organ of _Pachystomias microdon_ (after Von Lendenfeld). -L, lens; O, phosphorescent gland; P, pigment sheath.] - -But the power of emitting phosphorescent light is by no means confined -to the group of fishes. Some of the Macrurous Decapoda among the -Crustacea are known to be phosphorescent. In the case of _Heterocarpus -Alphonsi_, for example, the naturalists of the ‘Investigator’ found that -‘clouds of a pale blue highly luminous substance, which not only -illuminated the observers’ hands and surrounding objects in the vessel -in which the creature was confined, but also finally communicated a -luminosity to the water itself, were poured out apparently from the -bases of the antennæ.’ - -‘The _Willemoesia_, too, was luminous at two circumscribed points -somewhere near the orifices of the genital glands.’ - -Again, all the Alcyonarians dredged by the ‘Challenger’ in deep water -were found to be brilliantly phosphorescent when brought to the surface, -the light consisting, according to Moseley, of red, yellow, and green -rays only. - -Among the Echinoderms we have not many recorded instances of a -phosphorescent light being emitted, but it is quite possible that many, -if not all of them, may possess this power. The curious deep-sea form -_Brisinga_, that was first discovered by Ch. Asbjörnsen, is known to be -so brilliantly phosphorescent that it has been called a veritable -_gloria maris_, and writing of the curious brittle-star _Ophiacantha -spinulosa_ (dredged by the ‘Porcupine’ in 584 fathoms of water), -Professor Wyville Thomson remarks that the light was of a ‘brilliant -green, coruscating from the centre of the disc, now along one arm, now -along another, and sometimes vividly illuminating the whole outline of -the star-fish.’ - -According to Filhol many of the abysmal Annelid worms are in the habit -of emitting a vivid phosphorescent light, and capable thereby of -illuminating the medium in which they live. - -We have now considered all those characters exhibited by deep-sea -animals that may be associated with the absence of direct sunlight. To -run through them again briefly we may say: that the deep-sea species, -belonging to classes of animals that usually possess eyes, show some -modification in the size of their eyes, in that they are either very -large, very small, or altogether wanting. That deep-sea animals are -nearly always uniformly coloured. Very frequently they are black or grey -or white, less frequently bright red, purple, or blue. But whatever the -colour may be, spots, stripes, bands, and other markings of the body are -very rarely seen. That deep-sea animals are brilliantly phosphorescent, -the light being emitted either by special organs locally situated on the -head, body, or appendages, or by the general surface of the body. - -But there are some other characters that cannot be thus associated with -the absence of sunlight. - -In the first place bathybial fish, mollusca, crustacea, and other -animals usually possess a remarkably small amount of lime in their bones -and shells. - -In fishes we are told that the bones have a fibrous, fissured, and -cavernous texture, are light, with scarcely any calcareous matter, so -that the point of a fine needle will readily penetrate them without -breaking. In some the primordial cartilage is persistent in a degree -rarely met with in surface fishes, and the membrane bones remain more or -less membranous or are reduced in extent, like the operculum, which is -frequently too small to cover the gills. - -This cannot be due in all cases to a deficiency of carbonate of lime in -the sea water, for we find these characters well marked in some of the -fish, such as _Melanocetus Murrayi_, _Chiasmodus niger_, and _Osmodus -Lowii_, that are found on the Globigerina mud. - -Then again, the shells of the deep-sea Lamellibranchs, Gasteropods, -Brachiopods, and Crustacea are very frequently remarkably thin and -transparent, a character that is probably more generally due to a -weakness in absorptive or secretive activity than to a deficiency in the -supply of lime. - -There are one or two characters of the deep-sea fish that it is not easy -to account for, and it is necessary only to mention their occurrence -without attempting to offer any explanation of them. - -One of the most common of these is the very dark pigment occurring in -certain parts of the epithelium of the mouth and respiratory passages -and the endothelium of the peritoneum. For example, in _Bathysaurus -mollis_, living at a depth of 2,000 fathoms, the mouth and buccal -cavities are black. The same thing occurs in _Ipnops Murrayi_, and -indeed in all the strictly deep-sea forms. - -Another important character of very frequent occurrence is the reduction -in size, length, and number of the gill laminæ. - -Among invertebrates we may mention as a fact of some interest, dependent -perhaps on the soft character of the bottom, the preponderance of -stalked forms over those of more sessile habits. - -Thus among the Alcyonaria the characteristic forms of the deep water are -the Pennatulids, and more particularly the genus _Umbellula_ with its -long graceful stem and terminal tuft of polyps. Among the Echinoderma we -find many forms of stalked Crinoids. Among the Tunicates several curious -genera characterised by their long peduncles. - -Taking the fauna as a whole, Moseley regarded it as similar in some -respects to the flora of the high mountains. Some forms are dwarfed in -size, such as the species of Radiolaria, Cerianthus, some of the -Cephalopods, &c., while others are very much larger than their -shallow-water allies, such as the Pycnogonids, nearly all the Crustacea, -Alcyonarians (as regards the size of the polypes), Siphonophora, and -many others. - - - - - CHAPTER V - THE PROTOZOA, CŒLENTERA, AND ECHINODERMA OF THE DEEP SEA - - -The most important, but perhaps somewhat disappointing, result of the -deep-sea researches of recent years has been to prove that the abysmal -fauna does not possess many very extraordinary forms. - -It seemed probable, before the dispatch of the ‘Challenger’ expedition, -that when the dredge and the trawl should be successfully employed in -depths of over 2,000 fathoms, a new and remarkable fauna would be -brought to light. Some naturalists thought it even possible that, not -only would many genera be found alive that are known to us only by their -fossilised skeletons in the secondary and tertiary rocks, but that there -might be many other new creatures whose anatomy would throw much light -on the theories of the evolution of the animal series. - -But none of the great expeditions that have sailed since the year 1874 -have yet succeeded in showing that the hopes and wishes of these -naturalists were really justified. Although thousands of species of -animals have been described in the volumes that have been devoted to -deep-sea work, the number of the sub-kingdoms and classes remains the -same, and indeed the number of new families and genera has not been -increased in any very unprecedented manner. - -We have found no animals in the depths of the sea of such interest and -importance as Ornithorhynchus, Amphioxus, Balanoglossus, Peripatus, -Millepora, or Volvox among the living, or Hipparion, Archæopteryx, -Ammonites, Slimonia, and the Trilobites among extinct animals. - -The abysmal fauna is not in fact remarkable for possessing a large -number of primitive or archaic forms. It is mainly composed of a number -of species belonging to the families and genera of our shallow-water -fauna that have, from time to time, migrated into greater depths and -become modified in their structure in accordance with the extraordinary -conditions of their new habitat. - -There is very good reason to believe that this migration has been going -on from time immemorial, and consequently we find a few forms typical of -the bygone times, left to struggle for existence with the more recent -immigrants from shallow waters. But after all the proportion of ancient -forms to modern ones in the fauna of the abyss is not larger than it is -in the fauna of fresh-water lakes and streams or even of the dry land. -Nor is there any reason why it should be. The land and the fresh water -have been peopled by migrations from the shallow water of the sea from -generation to generation in precisely the same way, and they each can -show a certain number of archaic forms. - -We must now consider briefly some of the most interesting deep-sea -representatives of the various classes of the animal kingdom, referring -as we pass on to the extent to which these classes contribute to the -fauna of the abyss. - -We find a great difficulty in determining with any degree of certainty -the actual depths at which the supposed abysmal forms of Protozoa -actually live. All the Radiolaria and Foraminifera—the only Protozoa -that are largely represented in the fauna of the open seas—are -planktonic in habit; that is to say, they float or drift about in the -water without ever becoming attached to the sea bottom; and when the -contents of a dredge, that has been hauled up from a great depth, are -examined, it is impossible to say at what points in its long journey -from the bottom the Protozoa it contains were caught. Even if dredges -and nets are used which can be closed by a messenger at any particular -depth, the problem cannot be very easily settled; for even if the -protozoa shells that are captured are found to contain a certain amount -of protoplasm, it must be proved that that protoplasm is actually alive -when brought on deck before we know for certain that the species -actually live on the bottom. When the pelagic Foraminifera and -Radiolaria die and sink to the bottom, their protoplasm probably -disintegrates very slowly, and it is quite probable that the floor of -the ocean is littered with the shells of truly pelagic protozoa, each -containing a greater or smaller amount of undecomposed protoplasm. - -However, there is little doubt that there are some truly abysmal -Protozoa. Among the Radiolaria, for example, it seems extremely probable -that the majority of the Phæodaria and many Spumellaria live only in -very deep water. ‘A character common to these abyssal forms,’ says -Haeckel, ‘and not found in those from the surface or slight depths, is -found in their small size and massive heavy skeletons, in which respects -they strikingly resemble the fossil Radiolaria of Barbadoes and Nicobar -islands.’ The Phæodaria are very widely distributed over the floor of -the ocean, and occur in some districts in such numbers that the -‘Challenger’ was able to bring home some hundreds of thousands of -specimens. They are distinguished from other Radiolaria by the thick -outer and thin inner capsule, by the typical main opening or atropyle -placed on the oral pole of the main axis with a radiate operculum -provided with a tubular proboscis, and lastly by the presence of the -phæodium, a voluminous pigment body which lies invariably on the oral -half of the calymma and is composed of numerous singular pigment -granules of green, olive, brown, or black colour. - -[Illustration: FIG. 9.—_Challengeria Murrayi_, one of the Phæodaria -(2,250 fathoms). A, phæodium; B, central capsule; C, strands of -protoplasm in the calymma. After Haeckel.] - -There are many genera belonging to the Foraminifera that are very -probably inhabitants of abysmal depths, but they do not seem to possess -any special characters, unless it be a greater thickness and density of -their shells, to distinguish them from their shallow-water allies. - -Passing now to the group of the sponges or Porifera, we find that the -calcareous sponges are not represented at all in the abysmal zone. Two -species are found at a depth of 450 fathoms, but none are truly -bathybial in habit. The same remark applies to the horny sponges. -These forms chiefly belong to the littoral or very shallow-water -fauna, and never descend to greater depths than 400 fathoms. Of the -other groups of Porifera—the Monaxonia, the Tetractinellidæ, and the -Hexactinellidæ—several genera are known to extend down to some of the -greatest depths at which trawling operations have been successfully -carried on. It is difficult to point to any characters in these -sponges that can be attributed in any way to the conditions of -deep-sea life, but nevertheless we do find in deep water some of the -most remarkable and beautiful forms of sponge skeleton that can be -found anywhere. - -Amongst the Cœlentera we find in the deep water a remarkable sub-family -of Medusæ, which has been named by Haeckel the Pectyllidæ. It is -distinguished from the other jelly-fish by the curious sucking cups -situated at the ends of the tentacles. It seems probable that they are -used for purposes of locomotion, the animal walking over the muddy -bottom as on a series of stilts. - -Like most of the deep-sea Hydroids, the Pectyllidæ are usually devoid of -sense organs, but a single specimen of _Periphylla mirabilis_, captured -by the naturalists of the ‘Challenger,’ possessed well-marked eyes. - -There is also a peculiar family of the Siphonophora, called the -Auronectæ, consisting of a few specimens that have been hitherto found -only in very deep water. Like the well-known Portuguese man-of-war -_Physalia_ of the surface waters, the Auronectæ possess a large swimming -bladder or pneumatophore, but they have in addition another peculiar -bladder-like cavity, called the aurophore, communicating with it, which -may be an organ for secreting gas. - -A very interesting genus allied to Velella was also found in depths of -over 2,000 fathoms by the ‘Challenger’ expedition. It is supposed to be -a survival of the ancestral form of the Disconectæ, or, at any rate, to -be a link connecting the Siphonophora with the Medusæ. The very well -marked octoradial arrangement of the parts of _Discalia_, as this genus -has been termed, is certainly a point of great interest and importance. - -There is no large family of the sea anemones that is peculiar to deep -water, but several genera that occur only in the abyss exhibit some -curious modifications. The manner in which the tentacular pores have -become enlarged, and the tentacles themselves diminished in size and -flexibility, has already been referred to in a previous chapter (p. 36). - -The family of sea anemones that has been named the Corallimorphidæ, -characterised by the stiffness and slight contractility of the body, the -knobbed nature of the tentacles, and their distribution in several -series, was, until quite recently, considered to be a true abysmal -family. The two species, _Corallimorphus rigidus_ and _C. profundus_, -are known to occur only in very deep waters, and present some curious -modifications of structure in relation to their habit; but it seems -probable that to this family should be added the remarkable littoral -form _Thelaceros rhizophoræ_ found on the coast of Celebes attached to -the roots of the mangrove trees in the swamps. - -The fact that all the principal groups of the Actiniaria, except, -perhaps, the group that includes those forms with only eight -mesenteries, the Edwardsiæ, have representative genera or species in the -great depths of the ocean, points to the conclusion that the sea -anemones have migrated from the shallow waters in comparatively recent -times, and that the migrations have been successive, each period of -their history sending some specimens to survive or to become extinct in -the struggle for life in the deep sea. - -Of the Madreporarian corals, several genera are now known to inhabit -very deep water, but they do not present many very remarkable points of -divergence from the shallow-water forms. - -It is true that as we pass from the shallow waters, of those parts of -the world where the great colonial madrepores build up the greater part -of the vast coral reefs, into the deeper water beyond them, the solitary -forms become relatively more abundant, but no new groups characterised -by any special deep-sea attributes make their appearance. We must -remember, not only that a great many solitary corals occur in shallow -water in different parts of the world, but that some colonial forms, -such as _Lophohelia prolifera_ for example, are found only in very deep -water. - -Until quite recently it was usually stated in works dealing with the -structures of coral reefs that the so-called reef-building corals, that -is to say the large madrepores, astræids, and others, are confined to -water not deeper than thirty fathoms. This limit must now be somewhat -extended, in consequence of the discovery by Captain Moore of an -abundance of growing coral at a depth of forty-four fathoms in the China -seas; but, nevertheless, it is perfectly true that the corals do not -grow in such profusion in very deep water as to form anything that can -be compared with the reefs of the shores. It is quite possible that the -advantages afforded by the light, warmth, and abundance of food of the -shallow water may account for the luxuriance and vigour of the reef -corals, and that where the food is scarce, and the water cold and dark -as it is below fifty fathoms, the power of continuous gemmation is lost, -and the rapidity of the growth and reproduction of the individual polyps -is considerably diminished. - -The fact remains, however, that, as with the sea anemones, so with the -madrepores, nearly all the great divisions have a few isolated -representatives in the abyss, and that no great family occurring in -large numbers has yet been discovered peculiar to this zone. - -The Alcyonaria, on the other hand, do present us with at least one -example of a true deep-sea family. This great class of Anthozoa, -distinguished from the Zoantharia by the presence of not more than eight -tentacles and mesenteries and by the pinnate character of the former, -falls into four principal divisions. The Stolonifera, the Alcyonidæ, the -Gorgonidæ, and the Pennatulidæ. The first three of these divisions -principally inhabit the shallow water. Each of them sends a few -representatives into the great depths, but by far the greater number of -the genera and species are to be found between tide-marks or in depths -of less than fifty fathoms. - -The Pennatulids, on the other hand, are rarely found in very shallow -water, and nearly half the known genera live in deep water. At least two -families may be said to be characteristically abysmal. These are the -Umbellulidæ and the Protoptilidæ. - -The Pennatulidæ are regarded by naturalists as the most complicated or -highly organised group of the Alcyonaria. Three different forms of -polype build up the colony or sea-pen as it is called. There is a single -very much modified and enormously large polype, without tentacles, -forming the axis, a large number of ordinary Alcyonarian polypes -(autozooids) arranged in the form of leaves, or simply scattered -irregularly on the surface of the central polype, and a number of very -small undeveloped polypes (Siphonozoids) without tentacles, whose -function seems to be to pump water into the canals of the colony, and -thus to keep up the circulation of water. - -[Illustration: FIG. 10.—Umbellula Güntheri. Nat. size. After Agassiz.] - -The deep-sea genus _Umbellula_ possesses a very long and delicate axial -polype, and the Autozooids and Siphonozooids form a little cluster only -at its extreme summit. The small number of these polypes and the very -limited area over which they extend are the two most characteristic -features of the genus. It would take me too far into the anatomy of the -group if I were to add any further details; but I cannot pass on without -noting that the whole structure of Umbellula shows that it is far more -primitive and simple than the shallow-water genera. And, generally -speaking, this holds good for all the deep-sea Pennatulids. In fact, we -have here one of the rare examples of a series of genera, that can be -regarded as a slightly modified ancestry of the shallow-water genera, -that has been brought to light by the exploration of the abysmal depths -of the ocean. - -We have seen, then, that of the Cœlentera, the only order that has a -large proportion of its genera living in deep water, is the only one -whose members all possess a stalk by which they fix themselves into the -mud or sand at the bottom of the sea. - -It is not uninteresting to note, then, in passing on to the Echinoderma, -that the stalked Crinoids, the only Echinoderms that can permanently fix -themselves to the bottom, are nearly all found in deep water. - -Several years before the ‘Lightning’ was despatched on her memorable -pioneering voyage, Vaughan Thomson had proved that the common feather -star of the shallow waters of the British coasts passes through a stage -in its development which resembles the fossil genera of the order in -being provided with a stalk for attachment. - -But it was left for the naturalists of the ‘Porcupine,’ the -‘Challenger,’ the ‘Talisman,’ and other vessels employed in deep-sea -researches to prove that adult stalked Crinoids are still living in -nearly all parts of the world at the great depths of the sea. - -The genera of stalked Crinoids now living are the remains of a family -that at one time had many representatives in all parts of the world. -Nearly all the marine deposits of bygone epochs, including even those of -such remote periods as the Cambrian and Sub-Silurian, contain the -fossilised skeletons of these Crinoids. In some strata they are -represented by only a few genera, but in others they are found in such -enormous numbers that the seabeds of those early times must have been -literally carpeted with them. - -At the present day the few genera that survive have been driven from the -shore waters, and are chiefly found at depths of more than 200 fathoms, -a few only extending into 140 and even 70 fathoms. - -[Illustration: FIG. 11.—_Rhizocrinus lofotensis_, one of the deep-sea -stalked Crinoids. (After Carpenter.)] - -There are six genera known, and of these, two, _Hyocrinus_ and -_Bathycrinus_, are not found in less than 1,000 fathoms of water. - -There can be no doubt that these modern stalked Crinoids are closely -related to many of those that flourished in bygone periods of the -history of the earth. As Carpenter has pointed out, the family -Pentacrinidæ are remarkable for their long geological history. The genus -_Pentacrinus_ itself first appeared in the Trias and persisted through -the Secondary and Tertiary times to the present day. - -The general character of the fossil Pentacrinidæ is essentially the same -as that of their recent representatives, except that they often had much -longer stems which reached to a length of as much as 50 or even 70 feet; -while the number of arms was frequently limited to ten, which is not the -case in any recent species but _Pentacrinus naresianus_. - -But the deep-sea Echinoids, or sea-urchins, also present some features -of particular interest. Professor Agassiz in his report says, ‘One of -the very first results clearly indicated by the deep-sea dredgings of -Count Pourtales and the subsequent investigations of the “Porcupine” -expedition was the antique character of the new genera discovered in -deep water, and especially their resemblance to the cretaceous genera; -and the study of the “Challenger” Echinoids has brought this out still -more clearly.’ - -No fewer than twenty-four genera extend into the abysmal regions; of -these no less than sixteen, nearly all belonging to a new group of -Spatangoids, do not live at all in shallow water. - -The most interesting forms among these are the Pourtalesiæ, a group that -has existed since the Chalk. These are heart-shaped urchins with a very -peculiar test. ‘They all have large coronal plates, recalling the -Echini, with a disconnected apical system characteristic of many -cainozoic spatangoids; they have a sunken anal system, some of them a -most remarkable anal beak and a very striking pouch in which the mouth -is placed.’ They are found only in very deep water, and have no allies -among the modern littoral fauna. - -The genera _Calveria_ and _Phormosoma_ are two of the most abundant -Echinoids found in deep water, and they are both representatives of -forms that were very abundant in cretaceous times. They are remarkable -for the extreme flexibility of their shells. In shallow-water -sea-urchins the shells are composed of a great number of little plates -that fit so closely to one another that no movement is possible between -them. When the animal dies all the soft tissues decay and the shell -remains, to be tossed about by the waves until crunched or dashed to -pieces. In _Phormosoma_, however, the tiny plates of which the shell is -composed are freely movable on one another, and when the animal is alive -very considerable contractions and expansions can take place. - -None of the modern shallow-water Echinoids present this peculiarity, and -it is a very interesting and surprising fact that in this respect the -fossils of the chalk should resemble so closely the living urchins of -the abyss. - -But before leaving the Echinoids reference must be made to two more -points that have been made by the illustrious American naturalist. -Agassiz points out that all those genera that have the greatest -bathymetrical range, extending from the littoral to the abysmal region, -are at the same time genera which date back to the Cretaceous period, -while those having a somewhat more limited range go back to the -tertiaries, and those that extend only slightly beyond the littoral area -go back only to the later tertiaries. - -This interesting generalisation brings home to our minds the enormous -length of time that it must have taken these animals to migrate from the -shallow to the deep sea. In the struggles for existence between marine -animals it must always have been the last resort of those unable to -compete with the younger generations in shallow water to migrate into -the deeps. - -The scarcity of food, the darkness, and the pressure of these regions -can never be so favourable for the support of animals as the conditions -of the shores. We can well imagine that a species would take every -opportunity that is afforded to return from such inhospitable habitats, -and that only when, as it were, every door is closed, when no island, -continent, or cape can afford it a free scope for life in shallow water, -does it become a true deep-sea species. - -Steps taken towards the darkness in one period may be retrieved in the -next. The competing species may itself have become extinct or have moved -to another locality. Organs may have become modified or a new source of -food supply tapped which enable them to return once more to shallower -waters. No wonder that the steps in the progress, or rather retreat, to -the abyss have been the work of a time that can be counted only by -geological periods; and no wonder then at the remark made by many -deep-sea naturalists that the abysmal fauna becomes poorer the farther -it is from shallow water. - -The group of the Asteroidea, or star-fishes, contributes largely to the -fauna of the abyss. - -During the voyage of the ‘Challenger’ no fewer than 109 different -species were found in depths of over 500 fathoms, and in some localities -a very large number of star-fish were taken in one haul of the dredge. - -Nevertheless, there are not many abysmal genera that differ to any -remarkable degree from the littoral ones; and indeed it may be said that -the recent work on deep-sea Asteroids does not throw much new light -either on the phylogeny of the group or on their palæontological -history. - -The genus _Brisinga_, at one time supposed to be a connecting link -between the star-fishes and the brittle stars (Ophiurids), has recently -been shown to be closely related to the families Heliasteridea, -Echinasteridea, and others typical of the class Asteroidea; and, as -Sladen has pointed out, the peculiarities of structure that it exhibits -are probably due to its extreme isolation and the influence of its -abysmal habitats. - -But no work on the deep-sea fauna would be complete without some -reference to Brisinga. Discovered by Asbjörnsen in 1853, in 200 fathoms -of water in the Hardanger fjord, and described in a splendid memoir by -the elder Sars, it excited great interest among naturalists. The great -brilliancy of the phosphorescent light that it gave out on being brought -on deck, the remarkable tendency that it had to cast off some of its -numerous long, thin, ophiurid-like arms, and some of the general -features of its internal anatomy were points that were considered at the -time to be sufficient to justify the establishment of a separate -sub-order for the family Brisingidæ. - -The more recent discovery, however, of genera allied to Brisinga has -bridged over the gap separating it from other star-fish, and it is now -considered simply as the type of a family of the order. - -The numerous species of the genus that have been found since -Asbjörnsen’s original discovery are all inhabitants of deep water, some -of them going down to the enormous depth of 2,000 fathoms; indeed there -are very few genera in the animal kingdom, containing so many species as -the genus Brisinga, that have such a uniform deep-sea habitat. - -The last group of Echinoderms that we have to consider is the -Holothurians. It contains one order—the Elasipoda—that may be considered -to be truly bathybial, as there is only one species belonging to it, -_Elpidia glacialis_, that extends into water as shallow as fifty -fathoms. - -The Elasipoda are remarkable for their strongly-developed bilateral -symmetry. Adult Echinoderms as a rule possess a well-marked radial -symmetry, as we see exemplified in the feather-star, star-fish, and -sea-urchin, but this radial symmetry is only adopted when they undergo -their metamorphosis from the free swimming and bilaterally symmetrical -larval stage. They are not born radially symmetrical, but become so as -they grow up. Moreover, we must bear in mind that the radial symmetry of -the adult only obscures, it does not obliterate, the bilateral symmetry -of the larva. - -In the Holothurian, however, we can always discover a clear bilateral -symmetry even in the adult. That is to say, we can recognise an anterior -and a posterior end, a right and a left side of the body. It is an -organisation which emphasises, as it were, the anterior and posterior -ends, the right and left sides and the dorsal and ventral surfaces that -characterise this interesting deep-sea order, the Elasipoda. - -Here, then, we have an example of a character common to all the larvæ of -the sub-kingdom and exceptionally well marked in the adults of a family -confined to deep-sea habitats. - -Now we know that there is a tendency for some of the peculiar characters -of the ancestors of animals to be recapitulated in the course of their -development from the egg, and accordingly most naturalists are agreed -that all the Echinoderms have descended from some form of bilaterally -symmetrical ancestor. Are we, then, to believe that the Elasipoda -brought from the depths of the sea are more closely related to these -ancestral forms than the shallow-water families? - -The state of our knowledge at the present day hardly allows us to answer -this question very definitely. However nearly they are related to such -ancestral Echinoderms in general form, they are probably profoundly -modified by a deep-sea life. Nevertheless, in the simple shape of the -calcareous corpuscles of the skin, the simple form of the calcareous -ring, the communication of the water-vascular system with the exterior -by one or several pores, and in some other anatomical characters, they -give evidence of their primitive characters. - - - - - CHAPTER VI - THE VERMES AND MOLLUSCA OF THE DEEP SEA - - -It has not been my intention in this volume to confine my attention to -the truly abysmal forms, but rather to consider all those animals living -in deep water that show any characters strikingly different from their -relatives living in shallow water. - -The term deep water is, after all, only a relative one. - -To one accustomed only to shore collecting, ten fathoms is deep water, -while on the other hand, to such naturalists as those on board the -‘Challenger,’ who are accustomed to dredge in all seas, nothing under -1,000 fathoms is considered deep water. - -We must bear in mind, however, that at a depth of only 200 fathoms, the -conditions of life are very different to those of the shore waters. We -find a very great diminution in the amount of light, for instance, that -can penetrate through sea water teeming with floating organisms of all -kinds to reach the fauna attached to the bottom at such a depth. The -diminution in the amount of light must mean a diminution in the rapidity -of growth of chlorophyll-bearing plants, and consequently a diminution -in the food supplies of animals drawn from that source. - -We might expect then to find, even in such shallow water as this, some -forms of particular interest. It is true that the greater part of the -fauna is made up of ordinary shallow-water forms that have migrated -quite recently, and perhaps only temporarily, into the depths, but we -expect to find, and actually do find, the outposts of a new fauna. - -These remarks lead me to the consideration of one or two very remarkable -animals that have recently been brought to light. - -In that strange assembly of animals which, for want of a better word, -the authorities call the Vermes, there are three groups whose relations -to one another and to the other groups of Vermes have been and still -remain a puzzle to naturalists. - -These three groups are the Gephyrea, the Polyzoa, and the Brachiopoda. -In external form they are as different from one another as possible. - -The Gephyrea are solitary worm-like forms burrowing in the sand or -perforating rocks; the Polyzoa are minute creatures that frequently -build up by budding large colonies which assume in some cases dendritic -forms like corals, and the Brachiopoda are protected by thick bivalve -shells simulating in a striking manner the shells of the -Lamellibranchiate mollusca. - -But external form is not the only character that can be relied upon for -purposes of classification. The general and minute anatomy, together -with the story of the development of these animals, teach us that they -are in some way closely related. - -It is not within the scope of this book to enter into the discussion of -what these relations are; suffice it to say that the controversy has -within recent years to a great extent turned upon the position in our -classification of three interesting genera. These are Phoronis, -Rhabdopleura and Cephalodiscus. - -Phoronis occurs only in shallow water, Rhabdopleura has been found in -water from 40 to 200 fathoms deep off the Shetlands and on the Norwegian -coasts, while Cephalodiscus was discovered by the ‘Challenger’ at a -depth of 245 fathoms off Magellan Straits. - -Rhabdopleura forms colonies consisting of branched tubes growing upon -the tests of Ascidians, on sea-weeds, corals, or other objects fixed to -the sea bottom. In the open, free extremity of each of the branches may -be found the polypide attached to a filament or stalk which connects it -with the other polypides of the colony (fig. 12). - -[Illustration: FIG. 12.—A portion of a colony of _Rhabdopleura normani_. -(After Lankester.)] - -Each polypide is provided with a single pair of large pinnate arms, -resembling the arms of a Brachiopod, and a broad muscular epistome by -means of which it is able to creep up or down the tube. - -The affinities of this interesting creature are by no means sufficiently -well understood. It is one of those forms that, without being, strictly -speaking, a connecting link between large and well-known groups of -animals, indicates to us some of the lines of evolution that these -groups may have passed through; and, in so far as it does this, it has -its value and importance. - -Cephalodiscus, though related to Rhabdopleura in the presence of a -structure corresponding to the arms, and a broad epistome, seems to be -more closely connected with such a form as Balanoglossus in the presence -of a single pair of gill-slits, a small rudimentary notochord and the -position of the central nervous system.[2] - -Footnote 2: - - A rudimentary notochord projecting forward from the buccal cavity into - the epistome has quite recently been discovered in Rhabdopleura. - -[Illustration: FIG. 13.—A single polypide of _Rhabdopleura normani_. M, -mouth; B, epistome; S, polypide stalk. (After Lankester.)] - -Whatever position these genera may ultimately occupy in our systems of -classification, there can be little doubt that much valuable information -will be obtained by a further study of their structure and -development—information that will probably shed much light on the -relationships to one another of the many groups of Vermes. Their -occurrence in water of moderate depths only indicates perhaps that they -are gradually being crowded out from the more favourable localities of -shallow water, and are tending towards extinction on the one hand, or a -deep-sea habitat on the other. - -The Brachiopoda need not detain us long. Some species are capable of -existing at a great variety of depths without any observable -modification of shape or characters. Thus _Terebratulina caput -serpentis_ has the extraordinary bathymetrical distribution of 0–1,180 -fathoms, and _Terebratula vitrea_ 5–1,456 fathoms. _Atretia_ is the only -genus peculiar to deep water. It is a noteworthy fact in connection with -this order that the two genera, _Lingula_ and _Glottidia_, which compose -the sub-order Ecardines, are both confined to shallow water. Now the -Ecardines are anatomically, at any rate, the most primitive of the -Brachiopoda, and Lingula has the most ancient geological history of any -living genus of the animal kingdom, shells almost identical with those -of the living species being found abundantly in the Cambrian strata. Why -it is that Lingula has been able to maintain itself almost unchanged -through all the countless generations that have elapsed since Cambrian -times, and can now flourish amid the desperate struggle for existence in -the shallow waters of the tropics, while its companions, the corals, -mollusks, arthropods, &c., have changed or passed away, is one of those -problems in natural history that seem to us impossible of solution. The -time may come when we shall be able to appreciate better than we do now -the complicated relations between animals and their environment, and -then perhaps the peculiar fitness of Lingula will be made manifest; but -at present we can but mention the fact as a fact, and leave the solution -of the problem to the future. - -The order Gephyrea is probably another very ancient group of animals, -although in the absence of any hard calcareous, siliceous, or horny -skeleton the geological record can give us no confirmation of their -antiquity. As with the Brachiopods so with the Gephyrea, some of the -species have a very wide bathymetrical distribution. _Sipunculus nudus_, -for example, the commonest and best known of all the Gephyrea, extends -from quite shallow water to a depth of over 1,500 fathoms. As Selenka -has pointed out, it is those Gephyreans that live in holes in stones, or -in shells such as _Phascolion_ and _Phascolosoma_, that are more -frequently found at the greater depths; but, apart from this, there are -no characters that exclusively belong to the abysmal Gephyrea or are -more frequently found in them than in the shallow-water forms. Nor are -there any genera, at present brought to light, that are confined to -those regions of the sea. - -The group of the Annelida is not very well represented in the deep-sea -fauna. The genera _Serpula_ and _Terebella_ have been found very widely -distributed over the earth, at all depths from the shore to the abyss, -but there do not seem to be many genera that are confined to deep water. -In some cases, where there is a scarcity of lime in the water, the thin -protecting tubes of the sedentary forms are strengthened by the adhesion -of foreign particles, such as sponge spicules and arenaceous -foraminifera, but in others, the tubes are formed of successive layers -of a transparent quill-like substance (_Nothria Willemoesii_) which is -frequently armed with spiny projections. - -Most of the errant Polychætes found at great depths are said to be most -brilliantly coloured, and some of these, such as _Eunice amphiheliæ_, -have the power of emitting a bright phosphorescent light; but there seem -to be no very definite and constant characters separating these forms -from the Polychætes of shallow waters. - -As is the case with many other orders of animals, the species of -Annelida living in deep water are either blind or possess eyes of a -remarkably large size. _Genityllis oculata_ may be taken as an example -of a deep-sea annelid with large eyes. This annelid, belonging to the -family Phyllodocidæ, was found at a depth of 500 fathoms in the Celebes -sea. It possesses two enormous eyes which cover almost the whole of the -head, and there can be no doubt, from the investigations of Dr. Gunn on -their minute anatomy, that they are perfectly functional. - -Before leaving the Annelida a brief notice must be made of the very -extraordinary form _Syllis ramosa_, found parasitic on a hexactinellid -sponge at depths of about 100 fathoms. It is chiefly remarkable for the -very complicated manner it has of producing buds which do not -immediately become detached from the parent, but form a compound network -which ramifies through the interstices of the sponge like the colony of -a Hydromedusan. - -Passing now to the sub-kingdom Mollusca, we shall find that all the -classes are represented in the abysmal fauna. - -The Lamellibranchiata, or bivalves, occur in almost all depths of the -ocean, _Callocardia pacifica_ and _Callocardia atlantica_ having been -found at the enormous depth of 2,900 fathoms. Some species, such as -_Venus mesodesma_, have a very wide bathymetrical distribution, but -others are only known to occur in deep water. - -Concerning the characters of the deep-sea Lamellibranchiates, Mr. Smith, -in his report on the Lamellibranchia of the ‘Challenger’ expedition, -says ‘very deep-water benthal species certainly have a tendency to be -without colour, and of thin structure, no doubt resulting from the -absence of light the difficulty of secreting lime, the scarcity of food -and other unfavourable conditions of existence.’ But notwithstanding -this, the same author continues: ‘The species are apparently few in -number in comparison with those of shallow water; and new and peculiar -generic forms which we naturally expected would have been discovered are -of even still rarer occurrence.’ - -As in the group of the Lamellibranchia, so in the Gasteropoda, no very -remarkable new genera or species have been found in deep sea. Some -shallow-water genera, such as _Fusus_ for example, have representative -species in the abyss; but, with the exception of a want of brilliant -coloration and marking and a thinness of the shell, the deep-sea forms -do not exhibit any characteristic features. One of the most brightly -coloured shells found at great depths is that of _Scalaria mirifica_, -which is tinted rose and white, but this seems to be quite an -exceptional character among the deep-sea Gasteropods. Several new genera -were found in the deep water, but their general characters do not call -for any special remark. - -Among the Cephalopoda there seems to be little doubt that the genera -_Cirroteuthis_, _Bathyteuthis_, and _Mastigoteuthis_ are entirely -abysmal, and the same applies probably to one or two species of octopus; -but as Hoyle remarks, ‘apart from the single fact that _Bathyteuthis_ -and _Mastigoteuthis_ both have slender filiform tentacles with minute -suckers, no structural features have been discovered which will serve to -diagnose a deep-sea form from a shallow-water one.’ - -The exact habitat of the interesting genus _Spirula_ is unfortunately -still unknown. In some parts of the tropics the shores are covered with -spirula shells, and yet the animals that secrete them are still to be -reckoned amongst the greatest rarities of our museums. The numerous -dredgings of the ‘Challenger’ only brought to light one specimen of this -animal, and that from a depth of 360 fathoms, and the ‘Blake’ caught one -at a depth of 950 fathoms, so that there can be little doubt that -_Spirula_ lives in deep water. - -[Illustration: FIG. 14.—_Bathyteuthis abyssicola._ (After Hoyle.)] - -It seems to be very probable that some day, when the right place and -depth are discovered, _Spirula_ may be discovered in great abundance, -but we have at present no means of judging whether this will be in very -deep water or not. - -Almost precisely similar remarks apply to the distribution of the pearly -Nautilus. The shells of this Cephalopod are sometimes found in great -number on the shores of some of the islands of the Southern Pacific -Ocean and the Malay Archipelago, but the living animal is but rarely -captured. It has been asserted by some travellers that the pearly -Nautilus floats on the surface of the ocean and possesses the power of -suddenly diving to great depths on being disturbed; but it must be -remembered that Rumphius originally caught his Amboyna specimens of -Nautilus in traps set at a depth of 200 fathoms baited with sea-urchins, -and that the ‘Challenger’ captured a single living specimen off Matuku -island in 300 fathoms. - -The probability, then, is that both _Nautilus_ and _Spirula_ should be -included in the deep-sea fauna, but we are still in want of a great deal -more information concerning their life and habits before this point can -be definitely determined. - - - - - CHAPTER VII - THE ARTHROPODA OF THE DEEP SEA - - -The deep-sea fauna seems to be particularly rich in marine Arthropoda, -many curious and interesting forms being brought up with almost every -haul of the dredge. The Arthropoda, too, being very highly organised -animals, afford interesting and instructive examples of the effect of -abysmal life in the modification of the sense organs and the production -of varieties specially modified for the conditions of the struggle for -existence in their strange habitat. - -Concerning the groups of Ostracoda and Copepoda it may be said that the -evidence is not yet conclusive that they include any truly deep-sea -species. The largest known Ostracod, measuring somewhat more than an -inch in length and probably allied to the genus _Crossophorus_, has -quite recently been captured by Professor Agassiz at depths of less than -200 fathoms, but he could obtain no evidence that it descended into much -deeper water than this. - -Mr. Brady, in writing the report of the ‘Challenger’ Ostracoda, came to -the conclusion that they do exist in very limited numbers in the most -profound depths of the sea; but it is nevertheless quite possible that -all the Ostracods brought on deck by the trawl or dredge were really -captured either on the way down or on the way up, and are, strictly -speaking, pelagic in habit. - -Similar caution must be taken in dealing with the Copepoda, an order of -Crustacea that is essentially pelagic in habit. The only species that -has been regarded as undoubtedly abysmal is _Pontostratiotes -abyssicola_, a form whose carapace and antennæ are armed with -exceedingly long and strongly toothed spines, and was found in the mud -brought up by the trawl from a depth of 2,200 fathoms. - -_Calamus princeps_, the largest species of its genus of a deep reddish -brown colour, may also belong to the fauna of the deep sea, but we have -less evidence concerning the habitat of _Hemicalamus aculeatus_, -_Phyllopus bidentatus_, and some of the Euchætæ. - -The Amphipoda seem to be but poorly represented in the fauna of the -abyss; in fact it may be considered to be still an open question whether -any Amphipods habitually live in very deep water. - -In the reports on the ‘Challenger’ Amphipoda, the Rev. T. R. Stebbing -states that thirty-one specimens are known to come from great depths, -but it would be more correct to say that these specimens were found in -the dredges and trawls that had been lowered into the great depths. It -should be noticed, however, that some of these specimens do show -characters that suggest, at any rate, that they come from deep water. -Thus the genus _Lanceola_, for example, is characterised by the -smallness of the eyes and a soft membranous integument, while _Cystisoma -spinosum_, found in a dredge that had been at work at a depth of over a -thousand fathoms, has very large eyes. - -In his report on the Crustacea of the ‘Norske Nord-havns’ expedition, -Professor Sars gives a full description of many species of Amphipoda -brought by the dredge from depths of over 1,000 fathoms, and nearly all -of these were found to be quite blind. - -The form that seems to be most peculiar to the great depths of the -Northern Ocean is _Harpinia abyssi_. It was found at no less than -fifteen different stations at depths ranging from 350 to 2,215 fathoms, -and is characterised by its large size and the total absence of eyes. - -Another point that should be considered in coming to any conclusion on -the supposed habitat of such forms, is the similarity or dissimilarity -of widely distributed species. - -I have had occasion to point out in a previous chapter the general -similarity of the abysmal fauna all over the world, a very striking -phenomenon, commented on by almost every naturalist who has had a wide -experience of this kind of investigation. - -Among the Amphipoda we have a very striking example of this. The species -_Orchomene musculosus_ was taken by the ‘Challenger’ off the southern -part of Japan at a depth of 2,425 fathoms, the bottom being red clay and -the temperature 35·5° Fahr. The species _Orchomene abyssorum_ was taken -off the east coast of Buenos Ayres at a depth of 1,900 fathoms, the -bottom being blue mud and the temperature 33·1° Fahr. To the description -of this last-named species Mr. Stebbing adds, ‘had this species been -taken within reasonable distance of _O. musculosus_, the resemblance is -so great that one might have been tempted to disregard the points of -difference as due to some other cause than difference of species.’ - -Such a striking similarity between two species living so far apart from -one another may, when we take into consideration the depth, the -character of the bottom, and the temperature from which they are -supposed to have been dredged, be taken to support very strongly the -view that these species are really abysmal in habit. - -Among the Isopoda we have several very characteristic forms—no fewer -than nine distinct genera peculiar to the abysmal zone have been -described by Beddard—and of these two, _Bathynomus_ and _Anuropus_, are -to be regarded as types of sub-families. They seem to be very unevenly -distributed over the floor of the ocean, some regions, such as the whole -of the Central and Southern Atlantic and the Central and Western -Pacific, produce none; whilst the waters of the east coast of New -Zealand, the Crozets, and others, produce a great many varieties. Many -of the deep-sea Isopoda exhibit characters that are usually associated -with the bathybial life. Thus, according to Beddard, thirty-four of the -deep-sea species are totally blind, and eighteen have well-developed -eyes. In four species there are eyes which are evidently degenerating. -If we compare, for instance, the structure of the eye of _Serolis -schythei_, a species found in shallow water ranging from 4 to 70 -fathoms, with the eyes of _Serolis bromleyana_, a species living in deep -water ranging from 400 to 1,975 fathoms, we cannot fail to see that the -latter are undergoing a process of degeneration; the retinulæ and -pigment being absent, and nothing left of the complicated structure of -the Isopod eye but the remnants of the crystalline cones and corneal -facets (see figs. 4 and 5, p. 74). - -Taking the genus _Serolis_ alone, it has been said ‘that in all the -shallow-water forms the eye is relatively small but very conspicuous -from the abundant deposition of pigment; in all the deep-sea forms, with -the exception of _S. gracilis_, where the eye seems to be disappearing, -it is relatively larger but not so conspicuous, owing to the fact that -little or no pigment is present.’ - -In many groups of animals it has been shown that some of the deep-sea -species are relatively much larger in size than the shallow-water -species, and that others, more rarely, are much smaller, the abysmal -fauna reminding us in this respect of the characters of the alpine -flora. - -The Isopoda show many examples of this largeness in size, thus -_Bathynomus giganteus_, dredged by Professor Agassiz off the Tortugas at -a depth of over 900 fathoms, reaches the enormous size, for an Isopod, -of 9 inches (fig. 15). _Stenetrium haswelli_, again, is larger than any -of the shallow-water species of the genus, and the same remark applies -to the deep-sea species of the genus _Ichnosoma_, while _Iolanthe -acanthonotus_, from a depth of nearly 2,000 fathoms, is considerably -larger than most of the shallow-water Asellidæ. - -There is another very common character of deep-sea Crustacea that is -also well exemplified in the group of the Isopods, and that is the -extraordinary length and number of the spines covering the body. - -I have already referred to this character in the supposed deep-sea -Copepod _Pontostratiotes abyssicola_, and I shall have again to refer to -it in treating of the Decapoda and other groups of the Crustacea. - -Besides its enormous size _Bathynomus_ possesses some other characters -that may be correlated with its deep-sea environment. The respiratory -organs are quite different from those of other Isopods; instead of being -borne by the abdominal appendages, they are in the form of branched -outgrowths from the body-wall containing numerous blood-lacunæ, and the -appendages simply act as opercula to cover and protect them. The eyes of -the Bathynomus too are remarkably well developed, each one bearing 4,000 -facets, and they are directed not dorsally as in the Cymothoadæ, but -ventrally. The cause of these curious modifications of structure in -Bathynomus is by no means clear, but it is quite probable that they are -connected with the conditions of pressure and light in the deep sea. It -is a remarkable fact that the other deep-sea Isopods do not exhibit -precisely these modifications, and it might be supposed that the same -causes would produce the same or similar effects on the structure of -animals belonging to the same order. That is perfectly true, but we -cannot yet determine how long ago any one species has taken to a -deep-sea life, or what length of time, in other words, these conditions -have been at work in modifying the structure of the organism. A recent -immigrant into the abyss will naturally exhibit closer affinities with -its shallow-water allies than those that have dwelt in the region since -secondary or tertiary times. If we take this into consideration we -should expect to find considerable differences occurring between -deep-sea species of the same order, which is precisely what we do find. - -[Illustration: FIG. 15.—_Bathynomus giganteus._ From a depth of 1,740 -metres. (From Filhol.)] - -Concerning the Cirripedia, that curious group of profoundly modified -Crustacea that includes the barnacles and acorn shells, Dr. Hoek writes -in the ‘Challenger’ monograph:— - -‘Though unquestionably by far the greater part of the known Cirripedia -are shallow-water species, and though some of the species are capable of -living at a considerable variety of depths, as, for instance, -_Scalpellum stroemii_, yet it must be granted that the number of true -deep-sea species of Cirripedia is very considerable.’ Only two genera, -however, occur in depths of over 1,000 fathoms, and these—_Scalpellum_ -and _Verruca_—occur also as fossils in secondary and tertiary deposits. -The oldest of all fossil cirripedes, however, namely, _Pollicipes_, -never occurs, at the present day, in deep water, but is purely littoral -or neritic in habit. But what is perhaps more interesting still is the -fact, that, when we come to compare the living and the fossil species, -we find that in the one genus (_Scalpellum_) the deep-sea forms have -preserved the more archaic characters, and in the other (_Pollicipes_) -the shallow-water forms. - -Here then we are presented with a veritable puzzle for which we can at -present frame no manner of answer. Pollicipes on the one hand—like -Lingula among the brachiopods—has been able to maintain itself almost -unchanged amid the tremendous struggle for life of the shallow water of -the tropics ever since the Lower Oolite epoch; while Scalpellum, on the -other hand, has either become profoundly modified, or been driven into -the abysmal depths of the ocean. - -The group of the Thoracostraca, or stalk-eyed Crustacea, including -lobsters, crabs, hermit crabs, prawns, and shrimps, is well represented -in the deep sea. Most of them are characterised by being quite blind (in -many cases even the eye-stalks are obliterated), by being protected with -a dense covering of spines, by the thinness of their shells, and by -their bright red or carmine colour. - -The order Stomatopoda is almost entirely confined to the shallow waters -of the tropical or temperate shores. Not a single species is known to -inhabit the deep sea, and only a very few specimens have been captured -in more than a few fathoms of water. - -The Schizopoda, however, present us with many curious abysmal forms. -Most of the genera of this order belong to the pelagic plankton, and -many of them are known to possess the power of emitting a very strong -phosphorescent light. Several genera, however, such as _Gnathophausia_, -_Chlaraspis_, _Eucopia_, _Bentheuphausia_, &c., never seem to leave the -great depths of the ocean, and nearly all of these genera are -distinguished by being quite blind or possessing very much reduced or -rudimentary eyes. - -[Illustration: FIG. 16.—_Euphausia latifrons_, from the surface of the -sea. (After Sars.)] - -[Illustration: FIG. 17.—_Bentheuphausia amblyops_, from 1,000 fathoms. -(After Sars.)] - -If we compare, for example, the pelagic _Euphausia latifrons_ (fig. 16) -with the nearly allied but abysmal _Bentheuphausia amblyops_ (fig. 17), -the difference in this respect between a Schizopod living in the -sunlight and one living in the darkness of the deep-sea is very -apparent. - -The pelagic Schizopoda are usually quite pale and transparent; the -deep-sea forms on the other hand are frequently if not invariably of a -bright red colour, as is the case with many other deep-sea Crustacea to -which reference will be made later on. - -Passing on to the group of the Decapoda, we find that the most -interesting of all the abysmal cray-fish is the family of the Eryonidæ; -indeed, in some respects the discovery of these curious forms may be -reckoned among the most valuable results of the ‘Challenger’ Expedition. -They are characterised by the dorsal depression of the anterior part of -the cephalothorax, the absence of a rostrum, and the absence or very -rudimentary condition of the eyes (fig. 18). - -Their nearest relations seem to be certain genera of Crustacea that are -found in jurassic strata, in the lias, and more particularly in the -lithographic slates of Solenhofen. - -They have a very wide bathymetrical range extending from a depth of 250 -fathoms (_Polycheles crucifera_) to a depth of 2,000 fathoms -(_Willemoesia_). - -[Illustration: FIG. 18.—_Polycheles baccata_, one of the Eryonidæ. The -eyes and eye-stalks are absent, and the margin and sides of the carapace -armed with spines. (After Spence Bate.)] - -But there are many other curious forms of the macrurous crustacea that -deserve a passing mention. The graceful _Nematocarcinus gracilipes_, -distinguished by the extraordinary length of the antennæ and last four -pairs of legs, these appendages being three or four times the length of -the body, is by no means rarely met with in depths of over 400 fathoms. - -The genus _Glyphus_ captured by the ‘Talisman’ is remarkable for the -development of a peculiar pouchlike arrangement on the abdomen for the -protection of the larvæ during the younger stages of their existence. - -The proof of the existence of a peculiar cray-fish, _Thaumastocheles -zaleuca_, at a depth of 450 fathoms, was one of the most important -contributions to carcinology made by the ‘Challenger’ Expedition. The -chelæ of this remarkable form are of great but unequal length and armed -with long tooth-like spines giving it an appearance not unlike that of -the jaws of some carnivorous fish. The shell is soft and the abdomen -broad and flattened. There are no eyes nor even eye-stalks, but ‘in -front of the carapace,’ as Sir Wyville Thomson remarks, ‘between the -anterior and upper edge and the insertions of the antennæ, in the -position of the eyes in such forms as _Astacus fluviatilis_, there are -two round vacant spaces, which look as if the eye-stalks and eyes had -been carefully extirpated and the space they occupied closed with a -chitinous membrane.’ The deep-sea prawn, _Psalidopus_, recently taken in -500 fathoms of water by the ‘Investigator,’ affords us an example of a -common bathybial character, the whole body being covered with an -extraordinary array of sharp needle-like spines. - -Among the crabs many curious forms have been found in deep water -extending down to depths of over 2,500 fathoms. They are nearly all -characterised by blindness and a remarkable development of tooth-like -spines covering the carapace and limbs. - -The remarkable _Lithodes ferox_, from a depth of from 450 to 800 -fathoms, is perhaps the most perfectly armed crab—in the way of -spines—that exists. Every part of the body and limbs is so covered with -spines that one has to be extremely careful in handling even a dead -specimen. - -This is only one of the many examples that might be given to illustrate -this curious feature of the deep-sea Crustacea. Among the crabs alone we -have such forms as _Galathodes Antonii_, _Pachygaster formosus_, -_Dicranodromia mahyeuxii_ covered with a fierce armature of spines or -bristles; but there are nevertheless some species in which this -character is not particularly noticeable, and in these we usually find -some other protection against their enemies. An interesting example of -this has been described by A. Agassiz in a crab allied to the Maiadæ, -‘in which the dorsal face appears like a bit of muddy area covered by -corals, with a huge white arm resembling a fragment of an Isis-like -gorgonian.’ It is evident that this is a case in which the animal is -protected by its resemblance to the surroundings. - -The hermit crabs of the abyss, too, are not usually characterised by any -very great development of spines. They find their protection in the -shells they inhabit. Some of the deep-sea hermit crabs carry about with -them on their shells a sea anemone, as we find to be frequently the case -among the shallow-water species. _Pagurus abyssorum_, from a depth of -3,000 fathoms, is an example of this. - -In cases where there is a scarcity of gasteropod shells the hermit crabs -are obliged to find some other form of protection for their bodies. The -‘Blake’ found in the West Indies a hermit crab that had formed for -itself a case of tightly compressed sand, and another curious form, -named _Xylopagurus rectus_, makes its home in pieces of bamboo or in the -holes in lumps of water-logged wood. - -The last group of the Arthropoda we need refer to is that of the -Pycnogonida, those curious creatures seemingly made up entirely of legs, -and by some naturalists considered to be related to the Crustacea and by -others to the scorpions and spiders. - -Like the Brachiopoda the Pycnogonida are not usually found in greater -depths than 500 fathoms. Out of the twenty-seven known genera, only five -extend into the abyss, and not one of these can be called a true -deep-sea genus. - -There are three genera, _Nymphon_, _Collosendeis_, and _Phoxichilidium_, -that show a very wide distribution over the floor of the ocean, and are -capable of existing at the greatest depths, and of these the species of -the genus Nymphon have a truly remarkable range extending from the shore -to a depth of 2,225 fathoms. - -‘As a rule,’ says Hoek, ‘the deep-sea species are slender, the legs very -long and brittle, and the surface of the body smooth.’ They have -further, either no eyes at all or rudimentary eyes without pigment, and -in many cases—as, for example, _Collosendeis_—they are distinguished for -reaching to a gigantic size compared with their shallow-water relatives. - -The Tunicata is the group of animals that includes all those curious -vegetable-like organisms found upon our coasts that are familiarly known -as sea-squirts, or Ascidians, besides the salps, pyrosomas, and the -microscopic appendicularias of the pelagic plankton. - -[Illustration: FIG. 19.—_Collosendeis arcuatus_, from a depth of 1,500 -metres. (After Filhol.)] - -Notwithstanding the apparent simplicity of their adult structure, -naturalists are now agreed that they must be removed from the Mollusca, -with which they have hitherto been most frequently associated, and -placed in the group of the Vertebrata. It is the study of embryology -that has led to this unexpected conclusion, for we find, when we study -the larval forms, that they possess both a notochord and gill-slits, two -features that are characteristic of the group of the Vertebrata. - -The species of the group Perennichordata, which includes all those -Tunicates that possess a notochord persistent through life, are chiefly -pelagic in habit, the little creatures, rarely more than two or three -millimetres in length, swimming or drifting about with the sagittas, -copepods, ctenophores, and medusæ that compose the pelagic plankton. Fol -has recently described a gigantic form belonging to this group, reaching -a size of thirty millimetres in length, called _Megalocercus abyssorum_, -which he dredged from a depth of 492 fathoms; and other species have -been recorded down to a depth of 710 fathoms in the Mediterranean Sea. - -Among the simple Ascidians we find no family that is peculiar to deep -water; but the Cynthiidæ and Ascidiidæ both contain genera that are -abysmal, and the Molgulidæ have one species, _Molgula pyriformis_, that -extends into the abysmal zone to a depth of 600 fathoms. - -In the genus _Culeolus_ and in _Fungulus cinereus_ and _Bathyoncus_, all -deep-water Ascidians, there is a very curious modification of the -branchial sac, the stigmata being apparently not formed, in consequence -of the suppression of the fine inter-stigmatic vessels. This peculiar -feature is only found in the deep-sea simple Ascidians and, as we shall -see presently, in one species of the deep sea compound Ascidians, but it -is not apparently an essential character of those living in the abysmal -zone, notwithstanding the fact that it is found in such widely separated -genera; for _Corynascidia_, _Abyssascidia_, and _Hypobythius_, living in -depths lying between 2,000 and 3,000 fathoms below the surface, have -branchial sacs of the ordinary type. Professor Herdman is of opinion -that this simple form of branchial sac is not a primitive form, but most -probably a modification of a more complicated type. - -In _Culeolus Murrayi_ there is a remarkably abundant supply of -blood-vessels to the tunic, and these send special branches to a number -of small papilliform processes on its outer surface. This system of -highly vascular processes probably constitutes, as Professor Herdman -suggests, an additional or complementary respiratory apparatus. All -these modifications of the branchial system are of particular interest, -for we find so many instances of a similar kind among the inhabitants of -very deep water. I need only refer here to the modifications of this -system in the Isopod _Bathynomus_ already referred to (p. 129), and to -the reduction in the number of the gills of many of the deep-sea fishes. -Why there should be such modifications is a question upon which the -physical and natural history investigations of the conditions of life in -the great depths of the ocean at present throw no light. - -In a previous chapter I have referred to the fact that many of the -bathybial animals are characterised by being stalked. Among the simple -Ascidia we find many examples of stalked kinds living in deep water, -such as _Culeolus_ and _Fungulus_, but also several exceptions, such as -_Bathyoncus_, _Styela bythii_, and _Abyssascidia_, that are sessile. It -is a noteworthy fact, however, that the genus that has the most deep-sea -species—namely, _Culeolus_—is a genus that is provided with a very long -stalk. Furthermore, the only known stalked forms of the very large -family Ascidiidæ are the abysmal genera _Corynascidia_ and -_Hypobythius_. - -[Illustration: FIG. 20.—_Hypobythius calycodes._ G, nerve ganglion; H, -heart; M, the position of the atriopore. The large opening on the upper -side is the mouth. (From a drawing by Professor Moseley in Herdman’s -‘Tunicata of the “Challenger” Expedition.’)] - -The most remarkable character of the genus _Hypobythius_ is the simple -condition of its branchial sac, reminding one of the structure of this -organ in the shallow-water genus _Clavelina_. ‘There are no folds and -there are no internal bars,’ to quote the description given by Professor -Herdman; ‘only a single system of vessels can be recognised, branching -and anastomosing so as to form a close network, the small rounded meshes -of which are the stigmata. The tentacles and dorsal lamina cannot be -made out.’ - -Among the compound Ascidians only four families extend into the abysmal -zone, namely, the Botryllidæ, Polyclinidæ, Didemnidæ, and Cœlocormidæ, -and of these only one species, _Pharyngodictyon mirabile_, of the family -Polyclinidæ, extends into water of greater depth than 1,000 fathoms. In -_Pharyngodictyon_ we find the same curious simplification of the -branchial sac that we have just referred to in the genera of simple -Ascidians, _Culeolus_, _Fungulus_, and _Bathyoncus_. _Cœlocormus -Huxleyi_ from a depth of 600 fathoms is a very peculiar form and the -type of a separate family, the Cœlocormidæ. - -The free-swimming Tunicata included in the group _Ascidiæ salpiformes_, -which contains the genus _Pyrosoma_, and the order Thaliacea containing -the salps, are in all probability mainly confined to the surface waters. -A few specimens of _Pyrosoma_ were captured by the ‘Challenger’ dredges -which came up from very deep water, but it is doubtful at what point in -the journey to the surface the specimens entered the net. - -The most remarkable form of free-swimming Tunicate that has come to -light is _Octacnemus bythius_, a form that is probably allied to -_Salpa_. It was found twice, once in the dredge that came from a depth -of 1,070 fathoms, and once from 2,160 fathoms. The tunic of the animal -is gelatinous and hyaline, but the most important feature it possesses -is an imperforate membrane separating the branchial sac from the -peribranchial cavity. Octacnemus, in other words, possesses no true -stigmata, these structures being represented only by little pits in the -walls of the branchial sac. This curious and extremely interesting -modification of the respiratory organs points very strongly to the -conclusion that Octacnemus is truly a deep-sea animal. - - - - - CHAPTER VIII - THE FISH OF THE DEEP SEA - - -Of all the groups of animals that constitute the deep-sea fauna, the -fish show the greatest number of peculiarly abysmal characters. Being -much more highly differentiated than the invertebrates, they possess -more organs liable to undergo modifications of colour, size, and -structure, and consequently we are able to point to a great many more -features characteristic of deep-sea fish than we can do in any other -group of animals. - -The first point that calls for remark in the consideration of the fish -fauna of the deep sea is the almost entire absence of ancient and -primitive types. The Elasmobranchii, including the Sharks, Rays, and -Chimæra, constituting the order that from anatomical embryological -grounds is always regarded by naturalists as the most primitive order of -this class, is represented in very deep water by only one species. _Raia -hyperborea_ and _Chimæra monstrosa_, it is true, just enter into the -abysmal zone, but _Chimæra affinis_ is the only Elasmobranch that -extends to depths of over 1,000 fathoms. - -The Ganoidei too, the order that in palæozoic and mesozoic times was so -rich in genera and species, is entirely absent from the abysmal zone, -not a single representative having been found at any time by any of the -deep-sea expeditions. - -The Dipnoi, that remarkable order including the three fresh-water -genera, _Ceratodus_ from Australia, _Lepidosiren_ from Brazil, and -_Protopterus_ from West Africa, has no representative and no ally in the -deep waters of the ocean. - -The fishes of the deep sea, in fact, with only one or two exceptions, -all belong to the Order Teleostei, the most modern and most highly -differentiated order of the class, the families that are most fully -represented being the Macruridæ and then the Ophidiidæ and Gadidæ, and -the Berycidæ. - -At the limits of the katantic and abysmal zones, a large number of -families of Teleosteans entirely disappear, and as we approach the -deepest parts of the ocean, the number of fish that are found is -considerably reduced. As Dr. Günther very wisely remarks, ‘this -diminution in the number may be due to the difficulty of capturing -fishes at great depths, a difficulty which increases in proportion to -the depths at which the dredge is worked. But it must also be regarded -as evidence of the actually diminished variety of fishes.’ - -It may be interesting to the reader to give Dr. Günther’s table of the -number of species found at different depths, as it shows, among other -things, the marked change that occurs in the character of the fauna in -passing from the katantic to the abysmal zone. - - Between 100–300 fathoms, 232 species - Between 300–500 fathoms, 142 species - Between 500–700 fathoms, 76 species - Between 700–1,500 fathoms, 56 species - Between 1,500–2,000 fathoms, 24 species - Between 2,000–2,900 fathoms, 23 species - -As regards the general character presented by the deep-sea fishes, I -have already pointed out in the chapter dealing with the general -characters of the deep-sea fauna, the peculiarities in the size of the -eyes, the colours and markings of the body, and the texture of the bones -and muscles. There are, however, a few more characters of which mention -must be made. - -Notwithstanding the fact that all the abysmal fishes are carnivorous and -must consequently be capable—in the great number of cases—of rapid and -vigorous movement, the muscles of the trunk and tail are usually thin, -and the fascicles loosely connected with one another. - -Deep-sea fish are not characterised by an absence of the swimming -bladder. This organ occurs just as frequently and in the same families -as in the shallow-water fauna, but we do not know whether it possesses -any special peculiarities or not, as it is usually so ruptured and -destroyed by the change of pressure it undergoes in being brought to the -surface, that it is impossible to make any thoroughly accurate -investigation of its anatomy and relations. - -The extraordinary development of glands in the skin which secrete mucus, -and the presence in many forms of very highly specialised organs for -emitting phosphorescent light, are characters of the deep-sea fish -fauna, to which I have referred in a previous chapter. - -As with the Tunicates, some of the Crustacea and other groups, the fish -of the abysmal zone show curious modifications of the respiratory -system. The gill laminæ of these animals are not only reduced in number, -but appear to be short and shrunken. It is possible, of course, that -during life they may end in fine delicate points which are broken off or -ruptured during their capture, but still the horny rods that support -them are shorter than they are in shallow-water forms, and the general -evidence of their structure tends to show that they have undergone -profound modifications in the change to the conditions of deep-sea life. - -An extremely common and almost general character of deep-sea fishes is -the black coloration of some of the body cavities; this is limited to -the pharynx in many of the fishes that live about the hundred fathoms -limit, but the colour is more intense and spread all over the oral, -branchial, and peritoneal cavities in typical deep-sea forms. It may -seem very difficult at first to account for this remarkable development -of black pigment in parts of the body that are not usually, and, in some -cases, cannot at any time be exposed to view. It is obvious that it -cannot be functional as a hiding colour, either in offence or defence. -But it is quite possible that it is due to some modification of the -function of excretion. It is well known that in many cases of disease or -injury to the kidneys in vertebrates, the colour of the skin is -affected, and every one recognises now the fact that in many -invertebrates the colour of the skin is greatly dependent upon the -function of the secretion of the urates. - -It would at least be interesting to know if this dark coloration of the -mucous membranes is in any way correlated with any modification of the -structure or function of the kidneys. At present we have no recorded -observations on this point, but it is to be hoped that, when we have a -sufficient number of specimens brought home from the deep water, a -systematic investigation of this subject will be made. - -Lastly, it should be pointed out that our knowledge of the abysmal fauna -has not, at present, brought to light any evidence that the fish are of -an extraordinarily large size. In many groups of animals, as I have -frequently pointed out in the last few chapters, the large and gigantic -species or specimens are only found in the abyss. This may also be the -case with fishes, but we have no evidence that it is so. The only -methods that have been used at present for the investigation of the -fauna living on or near the floor of the deep oceans, are not of a kind -to lead to the capture of really large fish. That they may exist is -highly probable, but all that we know at present is, that the fish with -which we are acquainted living at great depths are not in any way -remarkable for their great size. - -Of the only two Elasmobranchs, one, namely _Raia hyperborea_, has been -found in water extending from 400 to 608 fathoms in depth. Only four -specimens have yet been taken, one by the Norwegian expedition off -Spitzbergen and three by the ‘Knight Errant’ off the northern coasts of -Scotland. It is interesting to find that this, the only deep-sea species -of the Rays, shows some striking peculiarities. ‘The teeth are -remarkably slender,’ says Günther, ‘small, irregularly and widely set, -different from those of other British Rays. In young specimens at any -rate those of the male do not differ from those of the female. The -mucous membrane behind the upper jaw forms a pad with a lobulated -surface. The mucous cavities of the head are extremely wide, and finally -the accessory copulatory organs have a spongy appearance, and are -flexible, the cartilage by which they are supported being a simple -slender rod.’ - -The other Elasmobranch, that extends into very deep water, is _Chimæra -affinis_, a species which can hardly be distinguished from the better -known _Chimæra monstrosa_, a fish that itself very frequently wanders -within the limits of the abysmal zone. - -Among the Teleostei, the family Berycidæ has several representatives in -the deep water. They are small fish rarely exceeding four inches in -length, with large heavy heads, with functional but small eyes, and an -abundant supply of large mucous glands on the skin. - -_Melamphaes beanii_, belonging to this family, has been captured at the -enormous depth of 2,949 fathoms. - -_Bathydraco antarcticus_, belonging to the family Trachinidæ, from a -depth of 1,260 fathoms, is an example of a true abysmal fish possessing -very large eyes. - -The Pediculati, the family of the anglers, is represented at depths of -over 2,000 fathoms by the interesting form _Melanocetus Murrayi_. The -eyes are very small indeed, the mouth huge and armed with long uneven -rasp-like teeth. At the end of the fishing-rod tentacle hanging over the -mouth, there is an organ that has been supposed to be capable of -emitting a phosphorescent light. This curious modification of the red -worm-like bait of the common shallow-water angler into a will-o-the-wisp -lantern attracting little fishes to their destruction in the deadly jaws -of the _Melanocetus_ is one of the most interesting adaptations that -have been brought to light by our study of the deep-sea fauna. - -Several species of the family Lycodidæ occur in the abysmal zone, but -they do not possess any features that call for special mention in this -place. - -[Illustration: FIG. 21.—_Melanocetus Murrayi_, 1,850–2,450 fathoms. -(After Günther.)] - -The family Ophidiidæ contributes very largely to the fish fauna of the -abyss. Some of the deep-water genera, such as _Neobythites_, have a wide -bathymetrical distribution extending from 100 fathoms to depths of over -2,000 fathoms, but others, such as _Bathyonus_, _Typhonus_, and -_Aphyonus_, only occur in depths of over 1,000 fathoms. - -The body is usually elongate and slender, ending in a pointed tail, the -head large and heavy, and the eyes, in the genera confined to the -abysmal zone, usually so far degenerated that they are not visible at -all from the outside. - -The Macruridæ form a family that contributes very largely to the -deep-sea fauna; no fewer than twenty-six different species are known to -occur within the limits of the abysmal zone. Not only do the Macruridæ -contribute a large number of different species, but they probably occur, -in some districts at any rate, in vast numbers. - -During the voyage of the ‘Talisman,’ for example, the French naturalists -caught in one haul of the dredge off the coast of Morocco in 500 fathoms -of water no fewer than 134 fish, of which number 95 belonged to the -family Macruridæ. - -They are usually small fish, measuring from a few inches to two feet in -length, with a body terminating in a long compressed tapering tail and -covered with spiny, keeled, or striated scales. - -The Pleuronectidæ or flat fish are not, as a rule, found in the abysmal -zone; one species, however, _Pleuronectes cynoglossus_, was found by the -American ship ‘Blake’ to extend into 732 fathoms of water. - -The families Sternoptychidæ and Scopelidæ are of particular interest to -us, as almost all the genera they contain belong either to the pelagic -or abysmal zones, and lend support to the view enunciated by Moseley, -that the deep-sea fauna has, partly at any rate, been derived from the -fauna of the pelagic zone. They are nearly all small slender fish with -delicate and frequently semi-transparent bodies, large gaping mouths -armed with numerous long irregular teeth, and frequently provided upon -the head and sides of the trunk with rows of eye-like phosphorescent -organs. - -These families, and others that have still to be referred to, belong to -the group of Teleostei that is called Physostomi, the name referring to -the open communication that usually exists in all these families between -the swimming bladder and the alimentary canal. It is a remarkable fact -that in none of the deep-sea representatives has this open communication -been discovered. It is true that many specimens are, when examined, so -lacerated by the diminution in pressure as to render anatomical study a -matter of difficulty, but still a fair number of uninjured -well-preserved specimens have now been examined and the duct has not -been found. - -Of the family Sternoptychidæ, _Gonostoma microdon_ has a most remarkable -distribution. It has been found at numerous stations in both the Pacific -and Atlantic Oceans at depths ranging from 500 to nearly 3,000 fathoms -of water. - -The Scopelidæ are represented by some very extraordinary types. The -genus _Bathypterois_, for example, occurring in depths ranging from 500 -to 2,500 fathoms, is characterised by the development of enormously long -pectoral fins to serve probably as organs of touch. ‘The rays of the -pectoral fin,’ says Dr. Günther, ‘are much elongated. The ventral fins -abdominal, with the outer rays prolonged, eight-rayed.... Gill rakers -long.’ They are further characterised by the absence of any true -phosphorescent organs and the smallness of their eyes. - -There can be little doubt, I think, that in these fishes the sense of -touch or taste to a great extent takes the place of the sense of sight -in other Scopelids. Not being provided with well-developed eyes or -phosphorescent organs to attract their prey, the pectoral fins and the -outer rays of the pelvic fins have become elongated and provided with -special sense organs for searching for their food in the fine mud of the -floor of the ocean. - -These long pectoral rays must have a very curious appearance in the -living fish. Mr. Murray observes: ‘When taken from the trawl they were -always dead, and the long pectoral rays were erected like an arch over -the head, requiring considerable pressure to make them lie along the -side of the body; when erected they resembled the Pennatulids like -Umbellula.’ Filhol considers that when the fish is progressing through -the obscurity of the abyss it probably carries these organs directed -forward, seeking with them in the mud for any worms or other animals -upon which it preys, or receiving through them warning of the approach -of an enemy from whom it is necessary to make an immediate escape. One -of the most remarkable of the deep-sea fish is closely related to -Bathypterois, namely _Ipnops Murrayi_, living in depths of over 1,000 -fathoms. It is about five inches long, of a yellowish brown colour, with -an elongated subcylindrical body covered with large thin deciduous -scales. There are no phosphorescent organs of the ordinary type met with -in the Scopelidæ, but upon the upper surface of the head there is found -a pair of organs somewhat resembling the ordinary eyes of fishes but -devoid of retina and optic nerve, that, from the researches of Moseley, -seem to be undoubtedly organs for emitting light. ‘The organs are paired -expanses, completely symmetrical in outline, placed on either side of -the median line of the upper flattened surface of the head of the fish, -extending from a line a little posterior to the nasal capsules nearly to -a point above the posterior extremity of the cranial cavity.’ They are -covered by the upper walls of the skull, which is extremely thin and -completely transparent in the region lying over them. ‘They are -membranous structures 0·4 mm. in thickness marked by hexagonal areas -about 0·04 mm. in diameter. When their surface is viewed by reflected -light the appearance is that of a number of glistening white isolated -short columns standing up in relief from its basal membrane.’ Each -hexagonal column is composed of a number of transparent rods disposed -side by side at right angles to the outer surface of the organ, with -their bases applied against the concave surface of a large hexagonal -pigment cell, one of which forms the basis of each hexagonal column. It -is still very doubtful what are the true homologies of this -extraordinary phosphorescent organ, but Moseley was of opinion that, ‘on -the whole, it seems not unlikely that the remarkable head organs of -Ipnops may be regarded as highly specialised and enormously enlarged -representatives of the phosphorescent organs on the heads of such allied -Scopelidæ as _Scopelus rafinesquii_ and _Scopelus metopoclampus_. It may -be conceived that in _Ipnops_ the supra-nasal and sub-ocular -phosphorescent organs of these species on either side have united and -become one with the result of the total obliteration of the eye.’ - -Most of the species of the genus _Scopelus_ are undoubtedly pelagic in -habit, descending during the day to depths of semi-darkness but rising -at night to the surface waters. It is not certain how many of the known -species occasionally or habitually dwell in very deep water, but there -seems to be no doubt that two species at least—_S. macrolepidotus_ and -_S. glacialis_—belong to the abysmal zone. Both of these species were -found in dredges that had been at work in depths of over 1,000 fathoms -and showed signs when examined of having been brought from the abyss. - -The Stomiatidæ are almost entirely confined to water from 450 to nearly -2,000 fathoms in depth. They may be distinguished from the Scopelidæ by -the long hyoid barbel close to the symphysis of the lower jaw, but like -many of the genera of that family they have wide gaping mouths armed -with a profusion of vicious looking teeth and a series of luminous spots -on the sides of the head and body. (_See_ Frontispiece.) - -In _Eustomias obscurus_, found in depths of over 1,000 fathoms in the -Atlantic by the ‘Talisman,’ the barbel is provided with a terminal -swelling, shaped like a dumb-bell, which may be capable of emitting a -phosphorescent light and serve the animal as a lure for the attraction -of its prey. The genus _Malacosteus_, too, presents us with some of the -most remarkable forms that are found in the abysmal zone. The mouth is -of enormous size and the integuments of the abdomen present very -definite longitudinal folds, leaving no doubt that this fish is able, -like several others living in deep water, to swallow prey of an enormous -size. - -But a perfectly unique structure in this fish ‘is a thin cylindrical -muscular band which connects the back part of the mandibular symphysis -with the hyoid bone. It is probably the homologue of a muscular band -which, in other Stomiatids, stretches on each side from the mandible to -the side of the hyoid, the two bands coalescing into an unpaired one in -_Malacosteus_. It is, in the present state of preservation, much -elongated, like a barbel, but during life it is notably contractile, and -serves to give to the extremity of the mandible the requisite power of -resistance when the fish has seized its prey, as without such a -contrivance so long and slender a bone would yield to the force of its -struggling victim.’ - -[Illustration: FIG. 22.—_Saccopharynx ampullaceus_; a deep-sea eel, with -the head of a large fish, which it has swallowed, showing through the -thin integuments of the body. (From Günther.)] - -Belonging to the family of the Salmons we find one genus _Bathylagus_ -that is undoubtedly an abysmal form. Although there may be some doubt as -to the exact depth at which the specimens were captured, the thinness of -the bones, the enormous size of the eyes, and other bathybial characters -prove that they must live in very deep water. Closely allied to the -salmon and the herrings is the family of the Alepocephalidæ, a family -that contributes several forms to the fauna of the deep sea, but they do -not possess any characters that call for special comment. Their vertical -distribution varies between 345 and 2,150 fathoms. - -The family Halosauridæ contains five species all confined to the abysmal -zone. They have long bodies tapering to a finely pointed tail, and the -head is provided with a snout that projects considerably in front of the -mouth. - -Of the family of the Eels there are several representatives in the deep -sea. They are characterised by a combination of true eel characters with -special modifications due to a bathybial existence. ‘To enable them to -seize upon prey more powerful than themselves certain organs have -undergone a degree of specialisation, as is observed in bathybial -members of other families with a similar mode of life; the jaws are -exceedingly elongate and the whole gape, the pharynx and stomach capable -of enormous distension.’ The head is very large, the eye very small and -the tail long and tapering (fig. 22). - -The lessons we learn from the study of the fishes of the deep sea are -particularly instructive. It would take far more space than can be -afforded here to fully illustrate all of the points that seem clear to -us, but I hope I have said sufficient to show that the fish fauna is -made up of genera and species belonging to several widely separate -families of the Teleostei; that some of them show, in a very marked way, -what may be looked upon as peculiarly bathybial characters, whilst -others are but slightly modified from their shallow-water -representatives. These facts by themselves lend support to the view that -the fauna of the deep sea has been derived from the fauna of shallower -water by successive migrations at different periods of the world’s -history. Those that exhibit in a most marked degree the special -bathybial characters are probably those whose immigration took place -long ago, whilst those more closely related to shallow-water forms are, -comparatively speaking, recent importations. The occurrence of Scopelidæ -and Sternoptychidæ in deep water suggests, as Moseley pointed out many -years ago, that the fauna is partly derived from the pelagic plankton. -But while these points may seem clear to us, there are others that still -require much more investigation and consideration. The whole question of -the function and use of the phosphorescent organs, the mucous glands, -the barbels and elongated fin rays, the mode of life, the deposition of -ova and their development, afford problems which in the present state of -our knowledge must remain unsolved. Let us hope that in the future there -may be a new stimulus given to deep-sea research, and these problems may -be again seriously studied and eventually solved. - - - - - INDEX - - - Actiniaria, 36, 93 - - —— two remarkable genera of, 15 - - _Aegir_, 15 - - Agassiz, A., - - —— on colour of Cœlentera, 65 - - —— on Echinoidea, 101, 103 - - Agassiz, L., on board the ‘Hassler,’ 12 - - ‘Albatross,’ American vessel, 15 - - Alcyonaria, 95 - - —— phosphorescence of, 81 - - Amphipoda, 124 - - Anemones - - —— of deep water, 36, 92 - - —— two remarkable genera of, 15 - - Annelida, 117 - - Ascidia compositæ, 146 - - —— salpiformes, 147 - - —— simplices, 142 - - Asteroidea, 104 - - - Barriers of temperature, 32 - - _Bathynomus_, 129 - - Beddard, F. E., on Isopoda, 127 - - Benthos, 53 - - Berycidæ, 154 - - ‘Blake,’ American vessel, 12 - - Blue mud, 42 - - Brachiopoda, 115 - - Brachyura, 138 - - _Brisinga_, 9, 105 - - Buchanan’s experiment, 19 - - - Carpenter, P. H., on Crinoidea, 100 - - _Cephalodiscus_, 113 - - Cephalopoda, 120 - - ‘Challenger,’ H.M.S., voyage of, 12 - - Cirripedia, 130 - - Cœlentera, - - —— colour of, 65 - - —— of deep sea, 91 - - Colour - - —— of the deep-sea fauna, 59, 66 - - —— of the deep-sea fish, 60 - - Copepoda, 124 - - Corals, 94 - - Crinoidea, 99 - - Crustacea, 123 - - —— colour of, 63 - - - Darkness of the abyss, 22 - - Diatom ooze, 39 - - Dipnoi, 149 - - - Echinoderma, 99 - - —— colour of, 64 - - Echinoidea, 101 - - Eels, 165 - - Elasipoda, 106 - - Elasmobranchii, 148, 153 - - Eryonidæ, 135 - - Eyes of abysmal animals, 67 - - —— of deep-sea crustacea, 72 - —— of deep-sea fish, 69 - - —— of deep-sea mollusca, 71 - - —— of _Genityllis_, 118 - - —— of _Neobythites_, 69 - - —— of _Serolis_, 73 - - - _Fenja_, 15 - - ‘Fish Hawk,’ American vessel, 12 - - Fol and Sarasin’s experiments, 25 - - Foraminifera, 90 - - Forbes, on the probable existence of a deep-sea fauna, 2 - - —— on zones of distribution, 49 - - - Ganoidei, 149 - - Gasteropoda, 119 - - Gephyrea, 116 - - Gills of deep-sea fish, 151 - - Globerigina ooze, discovery of, 5 - - —— distribution and composition of, 37 - - Green mud, 42 - - Gunn, Dr., on the eyes of _Genityllis_, 118 - - Günther, Dr., on deep-sea fish, 150 - - - Hall, Marshall, 12 - - Halosauridæ, 164 - - ‘Hassler,’ American ship, 12 - - Herdman, on Ascidians, 143, 146 - - Hermit crabs, 139 - - Hoek, Dr., on Cirripedia, 132 - - —— on Pycnogonida, 140 - - Holothuridea, 106 - - Hoyle, on Cephalopoda, 120 - - Hydroids, 92 - - - ‘Investigator,’ H.M.S., 16 - - _Ipnops Murrayi_, colour of, 60, 61 - - _Ipnops Murrayi_, phosphorescent organs of, 160 - - Isopoda, 127 - - - Katantic sub-zone, 50 - - ‘Knight Errant,’ H.M.S., 12 - - - Lamellibranchia, 119 - - ‘Lightning,’ H.M.S., 8, 9 - - Lime, scarcity of, in bones of bathybial fish, 83 - - —— in shells of mollusca, 83 - - Littoral sub-zone, 49 - - Lycodidæ, 155 - - - Macrura, 135 - - Macruridæ, 156 - - Madreporaria, 94 - - Medusæ, 91 - - Mollusca, 119 - - —— colour of, 62 - - Moore, Capt., 94 - - Moseley, H. N., on colour of Cœlentera, 65 - - —— on phosphorescent organs of _Ipnops_, 160 - - —— on the darkness of the abyss, 22 - - —— on the phosphorescence of Alcyonarians, 25 - - Murray, on _Bathypterois_, 159 - - - Nekton, 53 - - Neritic zone, 48 - - ‘Norma,’ Mr. Hall’s yacht, 12 - - Norske Nord-havns expedition, 7, 15 - - - Ophidiidæ, 156 - - Ostracoda, 123 - - - Packard, on the illumination of the abyss, 23 - - Pediculati, 155 - - Pelagic zone, 47 - - Pennatulidæ, 96 - - _Phoronis_, 111 - - Phosphorescence of Alcyonarians, 81 - — of deep-sea Crustacea, 80 - — of Echinoderma, 81 - - Phosphorescent light in the abyss, 24 - — organs of deep-sea fish, 77 - - Pigment in mucous membranes of deep-sea fish, 84, 152 - - Plankton, 52 - - Pleuronectidæ, 157 - - Polar currents, 30, 33 - - Polychæta, 118 - - ‘Porcupine,’ H.M.S., 8, 9 - - Porifera, 91 - - Pourtales, Count, 10 - - Pressure in the abyss, 19 - - Protozoa, 88 - - Pteropod ooze, 39 - - Pycnogonida, 139 - - - Radiolaria, 89 - - Radiolarian ooze, 39 - - Red mud, 37 - — — off the Brazilian coasts, 42 - - _Rhabdopleura_, 111 - - Ross, Sir James, on the fauna of the deep sea, 3 - - - Salmonidæ, 163 - - Sargasso sub-zone, 48 - - Sars, 6, 9, - — on Amphipoda, 125 - — on _Brisinga_, 105 - - Schizopoda, 133 - - Scopelidæ, 158 - - _Serolis_, 127 - - Siphonophora, 92 - - Size of deep-sea animals, 85 - — of fish, 153 - - Smith, Mr., on Lamellibranchia, 119 - - Spatangoids, 101 - - Sponges, 91 - - Stebbing, Rev. T. R., on Amphipoda, 125 - - Sternoptychidæ, 158 - - Stomatopoda, 133 - - Stomiatidæ, 162 - - - ‘Talisman,’ French vessel, 12 - - Teleostei, 149, 154 - - Temperature of the abyss, 28 - - Thomson, Sir Wyville, on _Pourtalesia_, 10 - — on _Thaumastocheles_, 137 - — on the darkness of the abyss, 22 - — on the phosphorescence of the sea, 26 - - Thoracostraca, 133 - - ‘Travailleur,’ French vessel, 12 - - ‘Triton,’ H.M.S., 12 - - Tunicata, 140 - - - Vegetable life, absence of, 42 - - Verrill, on the illumination of the abyss, 23 - - ‘Vittor Pessani,’ Italian vessel, 12 - - ‘Vöringin,’ Norwegian vessel, 14 - ------------------------------------------------------------------------- - - - - - MODERN SCIENCE SERIES. - - - _Edited by Sir JOHN LUBBOCK, Bart., M. P._ - - -I. =The Cause of an Ice Age.= - - By Sir ROBERT S. BALL, LL. D., F. R. S., Royal Astronomer of - Ireland. - -II. =The Horse:= - - A Study in Natural History. - - By WILLIAM HENRY FLOWER, C. 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He writes out -of the fullness of experimental knowledge, but his knowledge differs -from that of many a trained cultivator in that his skill in garden -practice is guided by a refined æsthetic sensibility, and his -appreciation of what is beautiful in nature is healthy, hearty, and -catholic. His record of the garden year, as we have said, begins with -the earliest violet, and it follows the season through until the -witch-hazel is blossoming on the border of the wintry woods.... This -little book can not fail to give pleasure to all who take a genuine -interest in rural life.”—_New York Tribune._ - - _THE ORIGIN OF CULTIVATED PLANTS._ By ALPHONSE DE CANDOLLE. 12mo. - Cloth, $2.00. - -“Though a fact familiar to botanists, it is not generally known how -great is the uncertainty as to the origin of many of the most important -cultivated plants.... In endeavoring to unravel the matter, a knowledge -of botany, of geography, of geology, of history, and of philosophy is -required. By a combination of testimony derived from these sources M. de -Candolle has been enabled to determine the botanical origin and -geographical source of the large proportion of species he deals -with.”—_The Athenæum._ - - _THE FOLK-LORE OF PLANTS._ By T. F. THISELTON DYER, M.A. 12mo. Cloth, - $1.50. - -“A handsome and deeply interesting volume.... In all respects the book -is excellent. Its arrangement is simple and intelligible, its style -bright and alluring.... To all who seek an introduction to one of the -most attractive branches of folk-lore, this delightful volume may be -warmly commended.”—_Notes and Queries._ - - _FLOWERS AND THEIR PEDIGREES._ By GRANT ALLEN, author of “Vignettes of - Nature,” etc. Illustrated. 12mo. Cloth, $1.50. - -“No writer treats scientific subjects with so much ease and charm of -style as Mr. Grant Allen. The study is a delightful one, and the book is -fascinating to any one who has either love for flowers or curiosity -about them.”—_Hartford Courant._ - -“Any one with even a smattering of botanical knowledge, and with either -a heart or mind, must be charmed with this collection of -essays.”—_Chicago Evening Journal._ - - _THE GEOLOGICAL HISTORY OF PLANTS._ By Sir J. WILLIAM DAWSON, F.R.S. - Illustrated. 12mo. Cloth, $1.75. - -“The object of this work is to give, in a connected form, a summary of -the development of the vegetable kingdom in geological time. To the -geologist and botanist the subject is one of importance with reference -to their special pursuits, and one on which it has not been easy to find -any convenient manual of information. It is hoped that its treatment in -the present volume will also be found sufficiently simple and popular to -be attractive to the general reader.”—_From the Preface._ - - _THE ICE AGE IN NORTH AMERICA, and its Bearings upon the Antiquity of - Man._ By G. FREDERICK WRIGHT, D. D., LL. D. With 152 Maps and - Illustrations. Third edition, containing Appendix on the - “Probable Cause of Glaciation,” by WARREN UPHAM, F.G.S.A., and - Supplementary Notes. 8vo. 625 pages, and complete Index. Cloth, - $5.00. - -“Prof. Wright’s work is great enough to be called monumental. There is -not a page that is not instructive and suggestive. It is sure to make a -reputation abroad as well as at home for its distinguished author, as -one of the most active and intelligent of the living students of natural -science and the special department of glacial action.”—_Philadelphia -Bulletin._ - - _THE GREAT ICE AGE, and its Relation to the Antiquity of Man._ By - JAMES GEIKIE, F.R.S.E., of H. M. Geological Survey of Scotland. - With Maps and Illustrations. 12mo. Cloth, $2.50. - -A systematic account of the Glacial epoch in England and Scotland, with -special reference to its changes of climate. - - _THE CAUSE OF AN ICE AGE._ By Sir ROBERT BALL, LL. D., F.R.S., Royal - Astronomer of Ireland, author of “Starland.” The first volume in - the MODERN SCIENCE SERIES, edited by Sir JOHN LUBBOCK. 12mo. - Cloth, $1.00. - -“An exceedingly bright and interesting discussion of some of the -marvelous physical revolutions of which our earth has been the scene. Of -the various ages traced and located by scientists, none is more -interesting or can be more so than the Ice age, and never have its -phenomena been more clearly and graphically described, or its causes -more definitely located, than in this thrillingly interesting -volume.”—_Boston Traveller._ - - _TOWN GEOLOGY._ By the Rev. CHARLES KINGSLEY, F.L.S., F.G.S., Canon of - Chester. 12mo. Cloth, $1.50. - -“I have tried rather to teach the method of geology than its facts; to -furnish the student with a key to all geology; rough indeed and -rudimentary, but sure and sound enough, I trust, to help him to unlock -most geological problems which may meet him in any quarter of the -globe.”—_From the Preface._ - - _AN AMERICAN GEOLOGICAL RAILWAY GUIDE._ Giving the Geological - Formation along the Railroads, with Altitude above Tide-water, - Notes on Interesting Places on the Routes, and a Description of - each of the Formations. By JAMES MACFARLANE, Ph. D., and more - than Seventy-five Geologists. Second edition, 426 pp., 8vo. - Cloth, $2.50. - -“The idea is an original one.... Mr. Macfarlane has produced a very -convenient and serviceable hand-book, available alike to the practical -geologist, to the student of that science, and to the intelligent -traveler who would like to know the country through which he is -passing.”—_Boston Evening Transcript._ - - - - - WORKS BY ARABELLA B. BUCKLEY (MRS. FISHER). - - - _THE FAIRY-LAND OF SCIENCE._ With 74 Illustrations. Cloth, gilt, - $1.50. - -“Deserves to take a permanent place in the literature of youth.”—_London -Times._ - -“So interesting that, having once opened the book, we do not know how to -leave off reading.”—_Saturday Review._ - - _THROUGH MAGIC GLASSES and other Lectures._ A Sequel to “The - Fairy-Land of Science.” Cloth, $1.50. - - _CONTENTS._ - - THE MAGICIAN’S CHAMBER BY MOONLIGHT. - MAGIC GLASSES AND HOW TO USE THEM. - FAIRY RINGS AND HOW THEY ARE MADE. - THE LIFE-HISTORY OF LICHENS AND MOSSES. - THE HISTORY OF A LAVA-STREAM. - AN HOUR WITH THE SUN. - AN EVENING WITH THE STARS. - LITTLE BEINGS FROM A MINIATURE OCEAN. - THE DARTMOOR PONIES. - THE MAGICIAN’S DREAM OF ANCIENT DAYS. - - _LIFE AND HER CHILDREN: Glimpses of Animal Life from the Amœba to the - Insects._ With over 100 Illustrations. Cloth, gilt, $1.50. - -“The work forms a charming introduction to the study of zoölogy—the -science of living things—which, we trust, will find its way into many -hands.”—_Nature._ - - _WINNERS IN LIFE’S RACE; or, The Great Backboned Family._ With - numerous Illustrations. Cloth, gilt, $1.50. - -“We can conceive no better gift-book than this volume. Miss Buckley has -spared no pains to incorporate in her book the latest results of -scientific research. The illustrations in the book deserve the highest -praise—they are numerous, accurate, and striking.”—_Spectator._ - - _A SHORT HISTORY OF NATURAL SCIENCE; and of the Progress of Discovery - from the Time of the Greeks to the Present Time._ New edition, - revised and rearranged. With 77 Illustrations. Cloth, $2.00. - -“The work, though mainly intended for children and young persons, may be -most advantageously read by many persons of riper age, and may serve to -implant in their minds a fuller and clearer conception of ‘the promises, -the achievements, and claims of science.’”—_Journal of Science._ - - _MORAL TEACHINGS OF SCIENCE._ Cloth, 75 cents. - -“The book is intended for readers who would not take up an elaborate -philosophical work—those who, feeling puzzled and adrift in the present -chaos of opinion, may welcome even a partial solution, from a scientific -point of view, of the difficulties which oppress their minds.”—_From the -Preface._ - - - - - Recent Volumes of the International Scientific Series. - - - _A HISTORY OF CRUSTACEA._ By Rev. THOMAS R. R. STEBBING, M.A., author - of “The Challenger Amphipoda,” etc. With numerous Illustrations. - 12mo. Cloth, $2.00. - -“Mr. Stebbing’s account of ‘Recent Malacostraca’ (soft-shelled animals) -is practically complete, and is based upon the solid foundations of -science. The astonishing development of knowledge in this branch of -natural history is due to the extension of marine research, the -perfecting of the microscope, and the general diffusion of information -regarding what has been ascertained concerning the origin of species.... -This volume is fully illustrated, and contains useful references to -important authorities. It is an able and meritorious survey of recent -crustacea.”—_Philadelphia Ledger._ - -“In all respects an admirable piece of work.”—_The Churchman._ - -“One of the most valuable and entertaining volumes in the series.... The -author is master of an engaging style, and offers words of cheer and -counsel to the beginner who may be dismayed by the bewildering riches of -the crustacean world. Every branch of the subject treated is presented -in the most interesting and significant light.”—_London Saturday -Review._ - - _HANDBOOK OF GREEK AND LATIN PALÆOGRAPHY._ By EDWARD MAUNDE THOMPSON, - D.C.L., Principal Librarian of the British Museum. With numerous - Illustrations. 12mo. Cloth, $2.00. - -“Mr. Thompson, as principal librarian of the British Museum, has of -course had very exceptional advantages for preparing his book.... -Probably all teachers of the classics, as well as specialists in -palæography, will find something of value in this systematic treatise -upon a rather unusual and difficult study.”—_Review of Reviews._ - -“A well-arranged manual from the hands of a competent authority.... Of -the nineteen chapters contained in the volume, seven deal with -preliminary topics, as the history of the Greek and the Latin alphabets, -writing materials, the forms of books, punctuation, measurement of -lines, shorthand, abbreviations, and contractions; five are devoted to -Greek palæography, seven to Latin.”—_The Critic._ - -“Covering as this volume does such a vast period of time, from the -beginning of the alphabet and the ways of writing down to the -seventeenth century, the wonder is how, within three hundred and -thirty-three pages, so much that is of practical usefulness has been -brought together.”—_New York Times._ - - _MAN AND THE GLACIAL PERIOD._ By G. FREDERICK WRIGHT, D.D., LL.D., - author of “The Ice Age in North America,” “Logic of Christian - Evidences,” etc. With numerous Illustrations. 12mo. Cloth, - $1.75. - -“The author is himself an independent student and thinker whose -competence and authority are undisputed.”—_New York Sun._ - -“It may be described in a word as the best summary of scientific -conclusions concerning the question of man’s antiquity as affected by -his known relations to geological time.”—_Philadelphia Press._ - -“The earlier chapters describing glacial action, and the traces of it in -North America—especially the defining of its limits, such as the -terminal moraine of the great movement itself—are of great interest and -value. The maps and diagrams are of much assistance in enabling the -reader to grasp the vast extent of the movement.”—_London Spectator._ - - - New York: D. APPLETON & CO., 1, 3, & 5 Bond Street. - ------------------------------------------------------------------------- - - - - - TRANSCRIBER’S NOTES - - - 1. P. 70, changed “japonicus” to “M. japonicus”. - 2. 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} - .ph1 { text-indent: 0em; font-weight: bold; font-size: xx-large; - margin: .67em auto; page-break-before: always; } - .ph2, .ph3 { text-indent: 0em; font-weight: bold; font-size: x-large; margin: .75em auto; } - .ph2 { page-break-before: always; } - .box {border-style: solid; border-width: medium; padding: 1em; margin: 0em auto; - page-break-inside: avoid; } - .vincula{ text-decoration: overline; } - .fraction {display: inline-block; vertical-align: middle; text-align: center; - font-size: smaller; text-indent: 0; } - .x-ebookmaker p.dropcap:first-letter { float: left; } - </style> - </head> - <body> - -<div style='text-align:center; font-size:1.2em; font-weight:bold'>The Project Gutenberg eBook of The fauna of the deep sea, by Sydney John Hickson</div> - -<div style='display:block; margin:1em 0'> -This eBook is for the use of anyone anywhere in the United States and -most other parts of the world at no cost and with almost no restrictions -whatsoever. You may copy it, give it away or re-use it under the terms -of the Project Gutenberg License included with this eBook or online -at <a href="https://www.gutenberg.org">www.gutenberg.org</a>. If you -are not located in the United States, you will have to check the laws of the -country where you are located before using this eBook. -</div> - -<div style='display:block; margin-top:1em; margin-bottom:1em; margin-left:2em; text-indent:-2em'>Title: The fauna of the deep sea</div> - -<div style='display:block; margin-top:1em; margin-bottom:1em; margin-left:2em; text-indent:-2em'>Author: Sydney John Hickson</div> - -<div style='display:block; margin:1em 0'>Release Date: January 24, 2021 [eBook #64380]</div> - -<div style='display:block; margin:1em 0'>Language: English</div> - -<div style='display:block; margin:1em 0'>Character set encoding: UTF-8</div> - -<div style='display:block; margin-left:2em; text-indent:-2em'>Produced by: Richard Tonsing, Sharon Joiner, Bryan Ness, and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive/American Libraries.)</div> - -<div style='margin-top:2em; margin-bottom:4em'>*** START OF THE PROJECT GUTENBERG EBOOK THE FAUNA OF THE DEEP SEA ***</div> - -<div class='tnotes covernote'> - -<p class='c000'><b>Transcriber’s Note:</b></p> - -<p class='c000'>The cover image was created by the transcriber and is placed in the public domain.</p> - -</div> - -<div class='nf-center-c0'> -<div class='nf-center c001'> - <div><span class='large'><b>Modern Science Series</b></span></div> - <div class='c002'><i>EDITED BY SIR JOHN LUBBOCK, BART., M. P.</i></div> - </div> -</div> - -<div class='section ph1'> - -<div class='nf-center-c0'> -<div class='nf-center c003'> - <div>THE FAUNA OF THE DEEP SEA</div> - </div> -</div> - -</div> - -<div id='Frontispiece' class='figcenter id001'> -<img src='images/frontispiece.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='fss'>STOMIAS BOA. HALF NATURAL SIZE. FROM A DEPTH OF 1,900 METRES. (AFTER FILHOL.)</span></p> -</div> -</div> - -<div class='titlepage'> - -<div> - <h1 class='c004'>THE FAUNA OF THE DEEP SEA</h1> -</div> - -<div class='nf-center-c0'> -<div class='nf-center c001'> - <div>BY</div> - <div class='c002'><span class='xlarge'>SYDNEY J. HICKSON, M. A.</span></div> - <div>(<span class='sc'>Cantab. et Oxon.</span>)</div> - <div><span class='small'>D.SC. (LOND.), FELLOW OF DOWNING COLLEGE, CAMBRIDGE</span></div> - <div class='c001'><i>WITH TWENTY-THREE ILLUSTRATIONS</i></div> - </div> -</div> - -<div class='figcenter id002'> -<img src='images/tpage_logo.jpg' alt='' class='ig001' /> -</div> - -<div class='nf-center-c0'> - <div class='nf-center'> - <div><span class='large'>NEW YORK</span></div> - <div><span class='large'>D. APPLETON AND COMPANY</span></div> - <div><span class='large'>1894.</span></div> - </div> -</div> - -</div> - -<div class='nf-center-c0'> -<div class='nf-center c003'> - <div><i>Authorized Edition.</i></div> - </div> -</div> - -<div class='chapter'> - <span class='pageno' id='Page_vii'>vii</span> - <h2 class='c005'>PREFACE</h2> -</div> - -<p class='c006'>The time may come when there will be no portion of -the earth’s surface that has not been surveyed and -explored by man.</p> - -<p class='c007'>The work of enterprising travellers has now been -carried on within a measurable distance of the North -Pole; the highest mountain ranges are gradually -succumbing to the geological surveyor; the heart of -Africa is giving up to us its secrets and its treasures, -and plans of all the desert places of the earth are -being made and tabulated.</p> - -<p class='c007'>The bottom of the deep sea was until quite -recently one of these terræ incognitæ. It was regarded -by most persons, when it entered into their -minds to consider it at all, as one of those regions -about which we do not know anything, never shall -know anything, and do not want to know anything.</p> - -<p class='c007'><span class='pageno' id='Page_viii'>viii</span>But the men of science fifty years ago were not -disposed to take this view of the matter. Pushing -their inquiries as to the character of the sea-fauna -into deeper and deeper water, they at length demanded -information as to the existence of forms of -animal life in the greatest depths. Unable themselves -to bear the heavy expenses involved in such -an investigation, they sought for and obtained the -assistance of the Government, in the form of national -ships, for the work, and then our knowledge of the -depths of the great ocean may be said to have commenced.</p> - -<p class='c007'>We know a good deal now, and in the course of -time we may know a great deal more, about this -interesting region; but it is not one which, in our -generation at any rate, any human being will ever visit.</p> - -<p class='c007'>We may be able to plant the Union Jack on the -summit of Mount Everest, we may drag our sledges -to the South Pole, and we may, some day, be able to -travel with ease and safety in the Great Sahara; but -we cannot conceive that it will ever be possible for -us to invent a diving-bell that will take a party of -explorers to a depth of three and a half miles of -<span class='pageno' id='Page_ix'>ix</span>water. We may complete our survey of the ocean -beds, we may analyse the bottom muds and name -and classify the animals that compose their fauna, -but there are many things that must remain merely -matters of conjecture. We shall never know, for -example, with any degree of certainty, how <i>Bathypterois</i> -uses its long feeler-like pectoral fins, nor -the meaning of the fierce armature of <i>Lithodes ferox</i>; -why the deep-sea Crustacea are so uniformly coloured -red, or the intensity of the phosphorescent light -emitted by the Alcyonaria and Echinoderms. These -and many others are and must remain among the -mysteries of the abyss.</p> - -<p class='c007'>Our present-day knowledge of the physical conditions -of the bottom of the deep sea and the animals -that dwell there is by no means inconsiderable.</p> - -<p class='c007'>It may be found in the reports of the scientific -expeditions fitted out by the English, French, German, -Italian, Norwegian, and American Governments, -in numerous volumes devoted to this kind of work, -and in memoirs and notes scattered through the -English and foreign scientific journals.</p> - -<p class='c007'>It is the object of this little book to bring together -<span class='pageno' id='Page_x'>x</span>in a small compass some of the more important facts -and considerations that may be found in this great -mass of literature, and to present them in such a -form that they may be of interest to those who do -not possess a specialist’s knowledge of genera and -species.</p> - -<p class='c007'>When it was found that animals can and do live -even at the greatest depths of the ocean, the interest -of naturalists was concentrated on the solution of -the following problems. Firstly, do the animals -constituting the fauna of the abyss exhibit any striking -and constant modification in correlation with the -physical conditions of their strange habitat? And, -secondly, from what source was the fauna of the -abyss derived? Was it derived from the shallow -shore waters, or from the surface of the sea? Is it -of very ancient origin, or the result of, comparatively -speaking, recent immigrations?</p> - -<p class='c007'>These questions cannot be answered in a few lines. -Any views that may be put forward regarding them -require the support of a vast array of facts and -figures; but as the limits of this little book would -not permit of my giving these, I have endeavoured -<span class='pageno' id='Page_xi'>xi</span>to select a few only of those which bear most directly -upon the points at issue.</p> - -<p class='c007'>To overburden my work with the names of genera -or the lists of species would not, it seemed to me, -either clear the issues or interest the general reader. -These may be found in the ‘Challenger’ monographs, -and other books dealing with the subject.</p> - -<p class='c007'>Those who wish to pursue the subject further will -find in the ‘Voyages of the “Blake,”’ by Alexander -Agassiz, an excellent and elaborate discussion of -deep-sea problems, and numerous illustrations of some -of the most interesting forms of abysmal life.</p> - -<p class='c007'>In Volume XXIII. of the ‘Bulletin of Comparative -Zoology’ the same author gives a most interesting -account of the deep-sea work that has recently -been done by the ‘Albatross’ expedition.</p> - -<p class='c007'>Filhol’s ‘<span lang="fr" xml:lang="fr">La Vie au Fond des Mers</span>’ is also a book -that contains a great deal of new and interesting -matter, together with some excellent coloured plates -of deep-sea animals.</p> - -<div class='c008'><span class='sc'>Sydney J. Hickson.</span></div> - -<div class='nf-center-c0'> - <div class='nf-center'> - <div><span class='sc'>Downing College, Cambridge</span>:</div> - <div><i>September, 1893</i>.</div> - </div> -</div> - -<div class='chapter'> - <span class='pageno' id='Page_xiii'>xiii</span> - <h2 class='c005'>CONTENTS</h2> -</div> - -<table class='table0' summary='CONTENTS'> -<colgroup> -<col width='10%' /> -<col width='83%' /> -<col width='5%' /> -</colgroup> - <tr> - <th class='c009'><span class='small'>CHAPTER</span></th> - <th class='c010'> </th> - <th class='c011'><span class='small'>PAGE</span></th> - </tr> - <tr> - <td class='c009'>I.</td> - <td class='c010'><span class='sc'>A Short History of the Investigations</span></td> - <td class='c011'><a href='#Page_1'>1</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>II.</td> - <td class='c010'><span class='sc'>The Physical Conditions of the Abyss</span></td> - <td class='c011'><a href='#Page_17'>17</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>III.</td> - <td class='c010'><span class='sc'>The Relations of the Abysmal Zone and the Origin of its Fauna</span></td> - <td class='c011'><a href='#Page_45'>45</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>IV.</td> - <td class='c010'><span class='sc'>The Characters of the Deep-sea Fauna</span></td> - <td class='c011'><a href='#Page_59'>59</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>V.</td> - <td class='c010'><span class='sc'>The Protozoa, Cœlentera, and Echinoderma Of the Deep Sea</span></td> - <td class='c011'><a href='#Page_86'>86</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>VI.</td> - <td class='c010'><span class='sc'>The Vermes and Mollusca of the Deep Sea</span></td> - <td class='c011'><a href='#Page_109'>109</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>VII.</td> - <td class='c010'><span class='sc'>The Arthropoda of the Deep Sea</span></td> - <td class='c011'><a href='#Page_123'>123</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>VIII.</td> - <td class='c010'><span class='sc'>The Fish of the Deep Sea</span></td> - <td class='c011'><a href='#Page_148'>148</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c012' colspan='2'><span class='sc'>Index</span></td> - <td class='c011'><a href='#Page_167'>167</a></td> - </tr> -</table> - -<div class='chapter'> - <span class='pageno' id='Page_xv'>xv</span> - <h2 class='c005'>LIST OF ILLUSTRATIONS</h2> -</div> - -<table class='table0' summary='LIST OF ILLUSTRATIONS'> -<colgroup> -<col width='7%' /> -<col width='72%' /> -<col width='20%' /> -</colgroup> - <tr> - <td class='c009'> </td> - <td class='c010'><span class='sc'>Stomias Boa. After Filhol, ‘<span lang="fr" xml:lang="fr">La Vie au Fond des Mers</span>’</span></td> - <td class='c011'><i><a href='#Frontispiece'>Frontispiece</a></i></td> - </tr> - <tr><td> </td></tr> - <tr> - <th class='c009'><span class='small'>FIG.</span></th> - <th class='c010'> </th> - <th class='c011'><span class='small'>PAGE</span></th> - </tr> - <tr> - <td class='c009'>1</td> - <td class='c010'><span class='sc'>Diagram illustrating the Passage of an Ocean Current across a Barrier</span></td> - <td class='c011'><a href='#Page_32'>32</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>2</td> - <td class='c010'><i>Sicyonis crassa.</i> <span class='sc'>After Hertwig, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_36'>36</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>3</td> - <td class='c010'><span class='sc'>Globigerina Ooze. After Agassiz, ‘Voyages of the “Blake”’</span></td> - <td class='c011'><a href='#Page_38'>38</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>4</td> - <td class='c010'><span class='sc'>Section through the Eye of</span> <i>Serolis schythei</i>. <span class='sc'>After Beddard, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_74'>74</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>5</td> - <td class='c010'><span class='sc'>Section through the Eye of</span> <i>Serolis bromleyana</i>. <span class='sc'>After Beddard, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_74'>74</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>6</td> - <td class='c010'><i>Opostomias micripnus.</i> <span class='sc'>After Günther, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_78'>78</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>7</td> - <td class='c010'><span class='sc'>Head of</span> <i>Pachystomias microdon</i>. <span class='sc'>After Von Lendenfeld, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_79'>79</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>8</td> - <td class='c010'><span class='sc'>Section through the Anterior Sub-orbital Phosphorescent Organ of</span> <i>Pachystomias microdon</i>. <span class='sc'>After Von Lendenfeld, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_80'>80</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'><span class='pageno' id='Page_xvi'>xvi</span>9</td> - <td class='c010'><i>Challengeria Murrayi.</i> <span class='sc'>After Haeckel, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_90'>90</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>10</td> - <td class='c010'><i>Umbellula Güntheri.</i> <span class='sc'>After Agassiz, ‘Voyages of the “Blake”’</span></td> - <td class='c011'><a href='#Page_97'>97</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>11</td> - <td class='c010'><i>Rhizocrinus lofotensis.</i> <span class='sc'>After Carpenter, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_100'>100</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>12</td> - <td class='c010'><i>Rhabdopleura normani.</i> <span class='sc'>After Lankester, ‘Contributions to our Knowledge of Rhabdopleura and Amphioxus’</span></td> - <td class='c011'><a href='#Page_112'>112</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>13</td> - <td class='c010'><span class='sc'>A Single Polypide of</span> <i>Rhabdopleura normani</i>. <span class='sc'>After Lankester</span>, <i>tom. cit.</i></td> - <td class='c011'><a href='#Page_114'>114</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>14</td> - <td class='c010'><i>Bathyteuthis abyssicola.</i> <span class='sc'>After Hoyle, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_121'>121</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>15</td> - <td class='c010'><i>Bathynomus giganteus.</i> <span class='sc'>After Filhol</span>, <i>tom. cit.</i></td> - <td class='c011'><a href='#Page_131'>131</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>16</td> - <td class='c010'><i>Euphausia latifrons.</i> <span class='sc'>After Sars, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_134'>134</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>17</td> - <td class='c010'><i>Bentheuphausia amblyops.</i> <span class='sc'>After Sars, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_134'>134</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>18</td> - <td class='c010'><i>Polycheles baccata.</i> <span class='sc'>After Spence Bate, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_136'>136</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>19</td> - <td class='c010'><i>Colossendeis arcuatus.</i> <span class='sc'>After Filhol</span>, <i>tom. cit.</i></td> - <td class='c011'><a href='#Page_141'>141</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>20</td> - <td class='c010'><i>Hypobythius calycodes.</i> <span class='sc'>After Moseley, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_145'>145</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>21</td> - <td class='c010'><i>Melanocetus Murrayi.</i> <span class='sc'>After Günther, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_156'>156</a></td> - </tr> - <tr><td> </td></tr> - <tr> - <td class='c009'>22</td> - <td class='c010'><i>Saccopharynx ampullaceus.</i> <span class='sc'>After Günther, ‘“Challenger” Reports’</span></td> - <td class='c011'><a href='#Page_164'>164</a></td> - </tr> -</table> - -<div class='section ph1'> - -<div class='nf-center-c0'> -<div class='nf-center c003'> - <div>THE FAUNA OF THE DEEP SEA</div> - </div> -</div> - -</div> - -<div> - <span class='pageno' id='Page_1'>1</span> - <h2 class='c005'>CHAPTER I<br /> <span class='large'>A SHORT HISTORY OF THE INVESTIGATIONS</span></h2> -</div> - -<p class='c006'>Our knowledge of the natural history of the deep -seas may be said to have commenced not more than -fifty years ago. There are, it is true, a few fragments -of evidence of a fauna existing in depths of -more than a hundred fathoms to be found in the -writings of the earlier navigators, but the methods -of deep-sea investigation were so imperfect in those -days that naturalists were disposed to believe that in -the abysses of the great oceans life was practically -non-existent.</p> - -<p class='c007'>Even Edward Forbes just before his death wrote -of an abyss ‘where life is either extinguished or -exhibits but a few sparks to mark its lingering -presence,’ but in justice to the distinguished naturalist -<span class='pageno' id='Page_2'>2</span>it should be remarked that he adds, ‘Its -confines are yet undetermined, and it is in the -exploration of this vast deep-sea region that the -finest field for submarine discovery yet remains.’</p> - -<p class='c007'>Forbes was only expressing the general opinion -of naturalists of his time when he refers with evident -hesitation to the existence of an azoic region. His -own dredging excursions in depths of over one -hundred fathoms proved the existence of many -peculiar species that were previously unknown to -science. ‘They were like,’ he says, ‘the few stray -bodies of strange red men, which tradition reports to -have been washed on the shores of the Old World -before the discovery of the New, and which served to -indicate the existence of unexplored realms inhabited -by unknown races, but not to supply information -about their character, habits, and extent.’</p> - -<p class='c007'>In the absence of any systematic investigation of -the bottom of the deep sea, previous to Forbes’s time -the only information of deep-sea animals was due -to the accidental entanglement of certain forms in -sounding lines, or to the minute worms that were -found in the mud adhering to the lead.</p> - -<p class='c007'>As far back as 1753, Ellis described an Alcyonarian -that was brought up by a sounding line from a depth -<span class='pageno' id='Page_3'>3</span>of 236 fathoms within eleven degrees of the North -Pole by a certain Captain Adriaanz of the ‘Britannia.’ -The specimen was evidently an <i>Umbellula</i>, and it is -stated that the arms (i.e. Polyps) were of a bright -yellow colour and fully expanded when first brought -on deck.</p> - -<p class='c007'>In 1819 Sir John Ross published an account of -his soundings in Baffin’s Bay, and mentions the existence -of certain worms in the mud brought from a -depth of 1,000 fathoms, and a fine Caput Medusæ -(Astrophyton) entangled on the sounding line at a -depth of 800 fathoms.</p> - -<p class='c007'>In the narrative of the voyage of the ‘Erebus’ and -‘Terror,’ published in 1847, Sir James Ross calls -attention to the existence of a deep-sea fauna, and -makes some remarks on the subject that in the light -of modern knowledge are of extreme interest. ‘I -have no doubt,’ he says, ‘that from however great a -depth we may be enabled to bring up the mud and -stones of the ocean, we shall find them teeming with -animal life.’ This firm belief in the existence of an -abysmal fauna was not, as it might appear from the -immediate context of the passage I have quoted, simply -an unfounded speculation on his part, but was evidently -the result of a careful and deliberate chain of -<span class='pageno' id='Page_4'>4</span>reasoning, as may be seen from the following passage -that occurs in another part of the same book:—‘It is -well known that marine animals are more susceptible -of change of temperature than land animals; indeed -they may be isothermally arranged with great -accuracy. It will, however, be difficult to get -naturalists to believe that these fragile creatures could -possibly exist at the depth of nearly 2,000 fathoms -below the surface; yet as we know they can bear the -pressure of 1,000 fathoms, why may they not of two? -We also know that several of the same species of -creatures inhabit the Arctic that we have fished up -from great depths in the Antarctic seas. The only -way they could get from one pole to the other must -have been through the tropics; but the temperature -of the sea in those regions is such that they could not -exist in it, unless at a depth of nearly 2,000 fathoms. -At that depth they might pass from the Arctic to the -Antarctic Ocean without a variation of five degrees -of temperature; whilst any land animal, at the most -favourable season, must experience a difference of -fifty degrees, and, if in the winter, no less than 150 -degrees of Fahrenheit’s thermometer—a sufficient -reason why there are neither quadrupeds, nor birds, -nor land insects common to both regions.’</p> - -<p class='c007'><span class='pageno' id='Page_5'>5</span>In the year 1845, Goodsir succeeded in obtaining -a good haul in Davis Straits, at a depth of 300 -fathoms. It included Mollusca, Crustacea, Asterids, -Spatangi, and Corallines.</p> - -<p class='c007'>In 1848, Lieutenant Spratt read a paper at the -meeting of the British Association at Swansea, on -the influence of temperature upon the distribution -of the fauna in the Ægean seas, and at the close of -this paper we find the following passage, confirming -in a remarkable way the work of previous investigators -in the same field. He says: ‘The greatest depth -at which I have procured animal life is 390 fathoms, -but I believe that it exists much lower, although the -general character of the Ægean is to limit it to 300 -fathoms; but as in the deserts we have an oasis, so in -the great depths of 300, 400, and perhaps 500 fathoms -we may have an oasis of animal life amidst the barren -fields of yellow clay dependent upon favourable and -perhaps accidental conditions, such as the growth of -nullipores, thus producing spots favourable for the -existence and growth of animal life.’</p> - -<p class='c007'>The next important discovery was that of the -now famous Globigerina mud by Lieutenants Craven -and Maffit, of the American Coast survey, in 1853, -by the help of the sounding machine invented by -<span class='pageno' id='Page_6'>6</span>Brooke. This was reported upon by Professor -Bailey.</p> - -<p class='c007'>Further light was thrown upon the deep-sea -fauna by Dr. Wallich in 1860, on board H.M.S. -‘Bulldog’, by the collection of thirteen star-fish living -at a depth of 1,260 fathoms.</p> - -<p class='c007'>Previous to this Torell, during two excursions to -the Northern seas, had proved the existence of an -extensive marine fauna in 300 fathoms, and had -brought up with the ‘Bulldog’ machine many forms -of marine invertebrates from depths of over 1,000 -fathoms; but it was not until 1863, when Professor -Lovén read a report upon Torell’s collections, that -these interesting and valuable investigations became -known to naturalists.</p> - -<p class='c007'>Nor must mention be omitted of the remarkable -investigations of Sars and his son, the pioneers of -deep-sea zoology on the coasts of Norway, who, by -laborious work commenced in 1849, failed altogether -to find any region in the deep water where animal -life was non-existent, and indeed were the first to -predict an extensive abysmal fauna all over the floor -of the great oceans. One of the many remarkable -discoveries made by Sars was <i>Rhizocrinus</i>, a stalked -Crinoid.</p> - -<p class='c007'><span class='pageno' id='Page_7'>7</span>Ever since that time the Norwegians and the -Swedes have been most energetic in their investigations, -and the publications of the results of the -Norske Nord-havns expeditions are regarded by all -naturalists as among the most valuable contributions -to our knowledge of the deep-sea fauna.</p> - -<p class='c007'>Notwithstanding the previous discovery of many -animals that undoubtedly came from the abysmal -depths of the ocean, there were still some persons who -found a difficulty in believing that animal life could -possibly exist under the enormous pressure of these -great depths. It was considered to be more probable -that these animals were caught by the dredge or sounding -lines in their ascent or descent; and that they -were merely the representatives of a floating fauna -living a few fathoms below the surface.</p> - -<p class='c007'>The first direct proof of the existence of an invertebrate -fauna in deep seas was found by the expedition -that was sent to repair the submarine cable of the -Mediterranean Telegraph Company. The cable had -broken in deep water, and a ship was sent out to -examine and repair the damage. When the broken -cable was brought on deck, it bore several forms of -animal life that must have become attached to it and -lived at the bottom of the sea in water extending -<span class='pageno' id='Page_8'>8</span>down to a depth of 1,200 fathoms. Among other -forms a <i>Caryophyllia</i> was found attached to the cable -at 1,100 fathoms, an oyster (<i>Ostrea cochlear</i>), two -species of Pecten, two gasteropods, and several worms.</p> - -<p class='c007'>The discoveries that had been made indicating -the existence of a deep-sea fauna led to the commission -of H.M. ships ‘Lightning’ and ‘Porcupine,’ and -the systematic investigation that was made by the -naturalists on these vessels brought home to the -minds of naturalists the fact that there is not only an -abysmal fauna, but that in places this deep-sea fauna -is very rich and extensive. The ‘Lightning’ was -despatched in the spring of 1868 and carried on its -investigations in the neighbourhood of the Faeroe -Islands, but the vessel was not suitable for the -purpose and met with bad weather. The results, -however, were of extreme importance; for, besides -solving many important points concerning the -distribution of ocean temperature, ‘it had been -shown beyond question that animal life is both -varied and abundant at depths in the ocean -down to 650 fathoms at least, notwithstanding the -extraordinary conditions to which animals are there -exposed.’</p> - -<p class='c007'>Among the remarkable animals dredged by the -<span class='pageno' id='Page_9'>9</span>‘Lightning’ were the curious Echinoderm, <i>Brisinga -coronata</i>, previously discovered by Sars, and the -Hexactinellid sponges, <i>Holtenia</i> and <i>Hyalonema</i>, the -Crinoids <i>Rhizocrinus</i> and <i>Antedon celticus</i>, and the -Pennatulid <i>Bathyptilum Carpenteri</i>, not to mention -numerous Foraminifera new to science.</p> - -<p class='c007'>In the spring of the following year, 1869, the -Lords Commissioners of the Admiralty despatched -the surveying vessel ‘Porcupine’ to carry on the work -commenced by the ‘Lightning.’</p> - -<p class='c007'>The first cruise was on the west coast of Ireland, -the second cruise to the Bay of Biscay, where dredging -was satisfactorily carried on to a depth of 2,435 -fathoms, and the third in the Channel between Faeroe -and Scotland.</p> - -<p class='c007'>The dredging in 2,435 fathoms was quite successful, -and the dredge contained several Mollusca, including -new species of <i>Dentalium</i>, <i>Pecten</i>, <i>Dacrydium</i>, &c., -numerous Crustacea and a few Annelids and Gephyrea, -besides Echinoderma and Protozoa. A satisfactory -dredging was also made in 1,207 fathoms.</p> - -<p class='c007'>The third cruise was also successful and brought -many new species to light, including the <i>Porocidaris -purpurata</i>, and a remarkable heart urchin, <i>Pourtalesia -Jeffreysi</i>.</p> - -<p class='c007'><span class='pageno' id='Page_10'>10</span>Concerning Pourtalesia Sir Wyville Thomson -says:—</p> - -<p class='c007'>‘The remarkable point is that, while we had so -far as we were aware no living representative of this -peculiar arrangement of what is called “disjunct” -ambulacra, we have long been acquainted with a fossil -family—the Dysasteridæ—possessing this character. -Many species of the genera Dysaster, Collyrites, &c., -are found from the lower oolite to the white chalk, but -there the family had previously been supposed to have -become extinct.’</p> - -<p class='c007'>The discovery of two new Crinoids led to the -anticipation that the Crinoidea, the remarkable group -of Echinoderma, supposed at the time to be on the -verge of extinction, probably form rather an important -element in the abysmal fauna.</p> - -<p class='c007'>One of the most interesting results was the -discovery of three genera in deep water, <i>Calveria</i>, -<i>Neolampas</i> and <i>Pourtalesia</i>, almost immediately after -they were discovered by Pourtales in deep water -on the coasts of Florida, showing thus a wide -lateral distribution and suggesting a vast abysmal -fauna.</p> - -<p class='c007'>A year before the ‘Lightning’ was despatched, -Count Pourtales had commenced a series of investigations -<span class='pageno' id='Page_11'>11</span>of the deep-sea fauna off the coast of Florida. -The first expedition started in 1867 from Key West -for the purpose of taking some dredgings between -that port and Havana. Unfortunately yellow fever -broke out on board soon after they started, and only -a few dredgings were taken. However, the results -obtained were of such importance that they encouraged -Pourtales to undertake another expedition and enabled -him to say very positively ‘that animal life exists at -great depths, in as great a diversity and as great an -abundance as in shallow water.’</p> - -<p class='c007'>In the following years, 1868 and 1869, the expeditions -were more successful, and many important -new forms were found in water down to 500 fathoms. -Perhaps the most interesting result obtained was the -discovery of <i>Bourguetticrinus</i> of D’Orbigny; it may -even be the species named by him which occurs fossil -in a recent formation in Guadeloupe.</p> - -<p class='c007'>By this time the interest of scientific men was -thoroughly excited over the many problems connected -with this new field of work. The prospect of obtaining -a large number of new and extremely curious -animals, the faint hope that living Trilobites, Cystids, -and other extinct forms might be discovered, and -lastly the desire to handle and investigate great -<span class='pageno' id='Page_12'>12</span>masses of pure protoplasm in the form of the famous -but unfortunately non-existent Bathybius, induced -some men of wealth and leisure to spend their time -in deep-sea dredging, and stimulated the governments -of some civilised countries to lend their aid -in the support of expeditions for the deep-sea -survey.</p> - -<p class='c007'>Mr. Marshall Hall’s yacht, the ‘Norma,’ was employed -for some time in this work, and an extensive -collection of deep-sea animals was made. About the -same time Professor L. Agassiz was busy on board the -American ship, the ‘Hassler,’ in continuing the work -of Count Pourtales, and later on the Germans fitted -out the ‘Gazelle,’ and the French the still more famous -‘Travailleur’ and ‘Talisman’ expeditions. Nor must -we omit to mention in this connection the cruise of -the Italian vessel, the ‘Vittor Pessani,’ nor those of -the British surveying vessels, the ‘Knight Errant’ -and the ‘Triton,’ and the American vessels, ‘The -Blake’ and the ‘Fish Hawk.’</p> - -<p class='c007'>But of all these expeditions, by far the most complete -in all the details of equipment, and the arrangements -made for the publication of the results, was -the expedition fitted out in 1873 by the British -Government. The voyage of H.M.S. ‘Challenger’ -<span class='pageno' id='Page_13'>13</span>is so familiar to all who take an interest in the -progress of scientific discovery, that it is not necessary -to do more than make a passing mention of it in this -place. The excellent books that were written by -Wyville Thomson, by Moseley, and by other members -of the staff, have made the general reader familiar with -the narrative of that remarkable cruise and the most -striking of the many scientific discoveries that were -made; while the numerous large monographs that -have been published during the past fourteen years -give opportunities to the naturalist of obtaining all -the requisite information concerning the detailed -results of the expedition.</p> - -<p class='c007'>The expenditure of the large sum of money upon -this expedition and the publication of its reports has -been abundantly justified. The information obtained -by the ‘Challenger’ will be for many years to come -the nucleus of our knowledge of the deep-sea fauna, -the centre around which all new facts will cluster, -and the guide for further investigations.</p> - -<p class='c007'>To say that the ‘Challenger’ accomplished all that -was expected or required would be to over-estimate -the value of this great expedition, but nevertheless it -is difficult for us, even now, thoroughly to grasp the -importance of the results obtained or to analyse and -<span class='pageno' id='Page_14'>14</span>classify the numerous and very remarkable facts that -were gained during her four years’ cruise.</p> - -<p class='c007'>It is, of course, impossible, in a few lines, to give -a summary of the more important of the Natural -History results of the ‘Challenger’ expedition. Besides -proving the existence of a fauna in the sea at -all depths and in all regions, the expedition further -proved that the abysmal fauna, taken as a whole, -does not possess characters similar to those of the -fauna of any of the secondary or even tertiary rocks. -A few forms, it is true, known to us up to that time -only as fossils, were found to be still living in the -great depths, but a large majority of the animals -of these regions were found to be new and specially -modified forms of the families and genera inhabiting -shallow waters of modern times. No Trilobites, no -Blastoids, no Cystoids, no new Ganoids, and scarcely -any deep-sea Elasmobranchs were brought to light, -but the fauna was found to consist mainly of -Teleosteans, Crustacea, Cœlentera, and other creatures -unlike anything known to have existed in Palæozoic -times, specially modified in structure for their life in -the great depths of the ocean.</p> - -<p class='c007'>In 1876 the <span class='fss'>S.S.</span> ‘Vöringin’ was chartered by -the Norwegian Government and was dispatched to -<span class='pageno' id='Page_15'>15</span>investigate the tract of ocean lying between Norway, -the Faeroe islands, Jan Mayen, and Spitzbergen. The -investigations extended over three years, the vessel -returning to Bergen in the winter months.</p> - -<p class='c007'>The civilian staff of the ‘Vöringin’ included -Professors H. Mohn, Danielssen, and G. O. Sars, and -the expedition was successful in obtaining a large -number of animals from deep water by means of the -dredge and tangles and by the trawl.</p> - -<p class='c007'>The results of this expedition have been published -in a series of large quarto volumes under the general -title of the Norske Nord-havns Expedition.</p> - -<p class='c007'>The most interesting forms brought to light by -the Norwegians are the two genera <i>Fenja</i> and <i>Aegir</i>, -animals possessing the general form of sea anemones -but distinguished from all Cœlenterates by the -presence of a continuous and straight gut reaching -from the mouth to the aboral pores which completely -shuts off the cœlenteron or general body cavity from -the stomodæum.</p> - -<p class='c007'>In more recent times the work has been by no -means neglected. With the advantage of employing -many modern improvements in the dredges and -trawls in use, the American steamer, the ‘Albatross,’ -has been engaged in a careful investigation of the -<span class='pageno' id='Page_16'>16</span>deep-sea fauna of the eastern slopes of the Pacific -Ocean, while at the same time Her Majesty’s surveying -vessel, the ‘Investigator,’ has been obtaining some -interesting and valuable results from a survey of the -deep waters of the Indian Ocean. But our knowledge -of this vast and wonderful region is still in its infancy. -We have gathered, as it were, only a few grains from -a great unknown desert. It is true that we may not -for many years, if ever, obtain any results that will -cause the same deep interest and excitement to the -scientific public as those obtained by the first great -national expeditions, but there are still many important -scientific problems that may be and will be -solved by steady perseverance in this field of work, -and if we can only obtain the same generous support -from public institutions and from those in charge -of national funds that we have received in the past -two decades, many more important facts will doubtless -be brought to light.</p> - -<div class='chapter'> - <span class='pageno' id='Page_17'>17</span> - <h2 class='c005'>CHAPTER II<br /> <span class='large'>THE PHYSICAL CONDITIONS OF THE ABYSS</span></h2> -</div> - -<p class='c006'>It is not surprising that the naturalists of the early -part of the present century could not believe in the -existence of a fauna at the bottom of the deep seas.</p> - -<p class='c007'>The extraordinary conditions of such a region—the -enormous pressure, the absolute darkness, the -probable absence of any vegetable life from want of -direct sunlight—might very well have been considered -sufficient to form an impassable barrier to the -animals migrating from the shallow waters and to -prevent the development of a fauna peculiarly its -own.</p> - -<p class='c007'>The fragmentary accounts of animals brought up -by sounding lines from great depths might, it is true, -have thrown doubts on the current views; but they -were not of sufficient importance in themselves, -nor were the observations made with such regard to -the possibility of error, as to withstand the critical -remarks that were made to explain them away.</p> - -<p class='c007'><span class='pageno' id='Page_18'>18</span>The absence of any evidence obtained by accurate -systematic research, together with the consideration -of the physical character of the ocean bed, were quite -sufficient to lead scientific men of that period to -doubt the existence of any animal life in water deeper -than a few hundred fathoms.</p> - -<p class='c007'>We now know, however, that there is a very -considerable fauna at enormous depths in all the -great oceans, and we have acquired, moreover, considerable -information concerning some of those -peculiar physical conditions of the abyss that fifty -years ago were merely matters of speculation among -scientific men.</p> - -<p class='c007'>The relation between animals and their environment -is now a question of such great interest and -importance that it is necessary in any description of -the fauna of a particular region to consider its -physical conditions and the influence that it may be -supposed to have had in producing the characteristics -of the fauna.</p> - -<p class='c007'>The peculiar physical conditions of the deep seas -may be briefly stated to be these: It is absolutely -dark so far as actual sunlight is concerned, the -temperature is only a few degrees above freezing -point, the pressure is enormous, there is little or no -<span class='pageno' id='Page_19'>19</span>movement of the water, the bottom is composed of a -uniform fine soft mud, and there is no plant life.</p> - -<p class='c007'>All of these physical conditions we can appreciate -except the enormous pressure. Absolute darkness -we know, the temperature of the deep seas is not an -extraordinary one, the absence of movement in the -water and the fine soft mud are conditions that we -can readily appreciate; but the pressure is far greater -than anything we can realise.</p> - -<p class='c007'>At a depth of 2,500 fathoms the pressure is, -roughly speaking, two and a half tons per square -inch—that is to say, several times greater than the -pressure exerted by the steam upon the piston of -our most powerful engines. Or, to put the matter in -other words, the pressure per square inch upon the -body of every animal that lives at the bottom of the -Atlantic Ocean is about twenty-five times greater -than the pressure that will drive a railway train.</p> - -<p class='c007'>A most beautiful experiment to illustrate the -enormous force of this pressure was made during the -voyage of H.M.S. ‘Challenger.’ I give the description -of it in the words of the late Professor Moseley.</p> - -<p class='c007'>‘Mr. Buchanan hermetically sealed up at both -ends a thick glass tube full of air, several inches in -length. He wrapped this sealed tube in flannel, and -<span class='pageno' id='Page_20'>20</span>placed it, so wrapped up, in a wide copper tube, -which was one of those used to protect the deep-sea -thermometers when sent down with the sounding -apparatus.</p> - -<p class='c007'>‘This copper tube was closed by a lid fitting -loosely, and with holes in it, and the copper bottom -of the tube similarly had holes bored through it. -The water thus had free access to the interior of the -tube when it was lowered into the sea, and the tube -was necessarily constructed with that object in view, -in order that in its ordinary use the water should -freely reach the contained thermometer.</p> - -<p class='c007'>‘The copper case containing the sealed glass tube -was sent down to a depth of 2,000 fathoms and -drawn up again. It was then found that the copper -wall of the case was bulged and bent inwards -opposite the place where the glass tube lay, just as if -it had been crumpled inward by being violently -squeezed.</p> - -<p class='c007'>‘The glass tube itself, within its flannel wrapper, -was found when withdrawn, reduced to a fine powder, -like snow almost. What had happened was that the -sealed glass tube, when sinking to gradually increasing -depths, had held out long against the pressure, -but this at last had become too great for the glass -<span class='pageno' id='Page_21'>21</span>to sustain, and the tube had suddenly given way and -been crushed by the violence of the action to a fine -powder. So violent and rapid had been the collapse -that the water had not had time to rush in by -means of the holes at both ends of the copper cylinder -and thus fill the empty space left behind by the -collapse of the glass tube, but had instead crushed -in the copper wall and brought equilibrium in that -manner. The process is exactly the reverse of an -explosion, and is termed by Sir Wyville Thomson an -“implosion.”’</p> - -<p class='c007'>It is but reasonable to suppose that the ability -to sustain this enormous pressure can only be acquired -by animals after generations of gradual migrations -from shallow waters. Those forms that are brought -up by the dredge from the depths of the ocean -are usually killed and distorted by the enormous -and rapid diminution of pressure in their journey -to the surface, and it is extremely probable that -shallow-water forms would be similarly killed and -crushed out of shape were they suddenly plunged -into very deep water. The fish that live at these -enormous depths are in consequence of the enormous -pressure liable to a curious form of accident. If, in -chasing their prey or for any other reason, they rise -<span class='pageno' id='Page_22'>22</span>to a considerable distance above the floor of the -ocean, the gases of their swimming bladder become -considerably expanded and their specific gravity -very greatly reduced. Up to a certain limit the -muscles of their bodies can counteract the tendency -to float upwards and enable the fish to regain its -proper sphere of life at the bottom; but beyond that -limit the muscles are not strong enough to drive -the body downwards, and the fish, becoming more -and more distended as it goes, is gradually killed -on its long and involuntary journey to the surface -of the sea. The deep-sea fish, then, are exposed to -a danger that no other animals in this world are -subject to, namely that of tumbling upwards.</p> - -<p class='c007'>That such accidents do occasionally occur is -evidenced by the fact that some fish, which are now -known to be true deep-sea forms, were discovered -dead and floating on the surface of the ocean long -before our modern investigations were commenced.</p> - -<p class='c007'>Until quite recently, every one agreed that no -rays of sunlight could possibly penetrate the sea -to a greater depth than a few hundred fathoms.</p> - -<p class='c007'>Moseley says that ‘probably all is dark below -200 fathoms excepting in so far as light is given out -by phosphorescent animals,’ and Wyville Thomson -<span class='pageno' id='Page_23'>23</span>speaks of the ‘utter darkness of the deep-sea -bottom.’</p> - -<p class='c007'>Within the last few years a few authors have -maintained that it is quite possible that a few rays -of sunlight do penetrate even to the greatest depths -of the ocean—a view mainly based on the fact that so -many deep-sea animals possess extremely perfect and -complicated eyes and very brilliant colours. Verrill -says: ‘It seems to me probable that more or less -sunlight does actually penetrate to the greatest depths -of the ocean, in the form of a soft sea-green light, -perhaps at 2,000 or 3,000 fathoms equal in intensity -to our partially moonlight nights and possibly at the -greatest depths equal only to starlight. It must be -remembered that in the deep sea far away from land -the water is far more transparent than near the coast.’ -Packard is of a similar opinion.</p> - -<p class='c007'>There seem to me to be very slight grounds for -this view. The fact that, comparatively speaking, -shallow-water fish avoid nets that are rendered -phosphorescent by entangled jelly-fish does not -justify us in assuming that deep-sea fish avoid -regions where there are phosphorescent Gorgonians -or Pennatulids. It is not by any means certain -that fish avoid sunken nets on account of their -<span class='pageno' id='Page_24'>24</span>phosphorescence. Most fish possess, as is well -known, a very acute sense of smell, and it is very -probable that they avoid such nets on account of -the putrid odours of the dead animals that remain -attached to them.</p> - -<p class='c007'>Nor is there much strength in the further -argument that it can hardly be possible that there -can be an amount of phosphorescent light regularly -evolved by the few deep-sea animals, having this -power, sufficient to cause any general illumination, or -powerful enough to have influenced, over the whole -ocean, the evolution of complex eyes, brilliant and -complex protective colours, and complex commensal -adaptations.</p> - -<p class='c007'>We have no sound information to go upon to be -able to judge of the amount of light given off by -phosphorescent animals at the bottom of the deep sea. -The faint light they show on deck after their long -journey from the depths in which they live to the -surface may be extremely small compared with the -light they give in their natural home under a pressure -of 2½ tons to the square inch. The complex eyes -that many deep-sea animals exhibit were almost -certainly not evolved as such, but are simple modifications -of eyes possessed by a shallow-water ancestry.</p> - -<p class='c007'><span class='pageno' id='Page_25'>25</span>The more recent experiments that have been -made, tend to show that no sunlight whatever penetrates -to a greater depth, to take an extreme limit, -than 500 fathoms.</p> - -<p class='c007'>Fol and Sarasin, experimenting with very sensitive -bromo-gelatine plates, found that there was no reaction -after ten minutes’ exposure at a depth of 400 -metres on a sunny day in March.</p> - -<p class='c007'>But although it is highly probable that not a -glimmer of sunlight ever penetrates to the depths -of the ocean, there is in some places, undoubtedly, a -very considerable illumination due to the phosphorescence -of the inhabitants of the deep waters.</p> - -<p class='c007'>All the Alcyonarians are, according to Moseley, -brilliantly phosphorescent when brought to the surface. -Many deep-sea fish possess phosphorescent -organs, and it is quite possible that many of the deep-sea -Protozoa, Tunicates, Jelly-fish, and Crustacea are -in their native haunts capable of giving out a very -considerable amount of phosphorescent light.</p> - -<p class='c007'>If we may be allowed to compare the light of -abysmal animals with that of surface forms, we can -readily imagine that some regions of the sea may -be as brightly illuminated as a European street is -at night—an illumination with many very bright -<span class='pageno' id='Page_26'>26</span>centres and many dark shadows, but quite sufficient -for a vertebrate eye to distinguish readily and at a -considerable distance both form and colour.</p> - -<p class='c007'>To give an example of the extent to which the -illumination due to phosphorescent organisms may -reach, I may quote a passage from the writings of -the late Sir Wyville Thomson.</p> - -<p class='c007'>‘After leaving the Cape Verde Islands the sea -was a perfect blaze of phosphorescence. There was -no moon, and although the night was perfectly clear -and the stars shone brightly, the lustre of the heavens -was fairly eclipsed by that of the sea. It was easy -to read the smallest print, sitting at the after-port in -my cabin, and the bows shed on either side rapidly -widening wedges of radiance so vivid as to throw the -sails and rigging into distinct lights and shadows.’</p> - -<p class='c007'>A very similar sight may frequently be seen in -the Banda seas, where on calm nights the whole -surface of the ocean seems to be a sheet of milky fire. -The light is not only to be seen where the crests of -waves are breaking, or the surface disturbed by the -bows of the boat, but the phosphorescence extends -as far as the eye can reach in all directions. It is -impossible, of course, to say with any degree of certainty -whether phosphorescence such as this exists at -<span class='pageno' id='Page_27'>27</span>the bottom of the deep sea, but it is quite probable -that it does in some places, and hence the well-developed -eyes and brilliant colours of some of the -deep-sea animals.</p> - -<p class='c007'>On the other hand the entire absence or rudimentary -condition of the eyes of a very considerable proportion -of deep-sea animals seems to prove that the -phosphorescent illumination is not universally distributed, -and that there must be some regions in -which the darkness is so absolute that it can only be -compared with the darkness of the great caves.</p> - -<p class='c007'>It is difficult to believe that the eyes of such -animals as crabs and prawns for example would -undergo degeneration if there were a glimmer of light -in their habitat, a light even so faint as that of a starlight -night in shallow water. With the faintest light -the eyes would be of use to them in seeking their -prey, avoiding their enemies, and finding their mates, -and any diminution in the keenness of this sense -would probably be of considerable disadvantage to -them and tend to their ultimate extinction.</p> - -<p class='c007'>It might be argued that the animals of the abysses -of the ocean probably feed chiefly upon the carcases -of pelagic animals that have fallen from the upper -regions of the sea, and that the sense of smell is -<span class='pageno' id='Page_28'>28</span>probably the most important for them in searching for -their food. That is quite probable; but many shallow-water -animals invariably seek their food by their -sense of smell without showing any traces of a weakness -in their sense of sight. It may be taken as an -axiom of biology that unless a particular sense is -absolutely useless to an animal or a positive disadvantage -to it, that sense will be retained.</p> - -<p class='c007'>It may be stated then with some confidence that -in the abysmal depths of the ocean there is no trace -of sunlight. It is highly improbable, on the face of -it, that any ray of light could penetrate through a -stratum of water four miles in thickness, even if the -water were perfectly pure and clear, but when we -remember that the upper regions, at least, are crowded -with pelagic organisms provided with skeletons of -lime and silica, we may justly consider that it is impossible.</p> - -<p class='c007'>The temperature of the water in the abyss is by -no means constant for a constant depth nor does it -vary with the latitude. It is true that, as a rule, the -water is colder at greater depths than in shallower ones, -and that the deeper the thermometer is lowered into -the sea, the lower the mercury sinks. This is consistent -with physical laws. If there is any difference at -<span class='pageno' id='Page_29'>29</span>all in the temperature of a column of water that has -had time to settle, the thermometer will always reach -its highest point at the top of the column and its -lowest at the bottom, for the colder particles being -of greater specific gravity than the warmer ones will -sink, and the warmer ones will rise.</p> - -<p class='c007'>The truth of this will be clear if we imagine a -locality at the bottom of a deep ocean with a source -of great heat such as an active volcano.</p> - -<p class='c007'>Such a source of heat would, it is true, raise the -temperature of the water in its immediate vicinity, -but the particles of water thus heated would immediately -commence to rise through the superjacent -layers of colder water, and colder particles would fall -to take their places. Thus the effect of an active -volcano at the bottom of the deep sea would not -be apparent at any very great distance in the same -plane. In fact, unless the bottom of the ocean was -closely studded with volcanoes we should expect to -find, as indeed we do find, that the temperature of -the sea rises as the water shallows.</p> - -<p class='c007'>If then we were to consider a great ocean as -simply a huge basin of water, we should expect to -find the water at the surface warmer than the water -at the bottom. The temperature of the surface -<span class='pageno' id='Page_30'>30</span>would vary constantly with the temperature of the -air above it. That is to say, it would be warmer at -the equator than in the temperate regions. The -temperature at the bottom would be the same as the -lowest temperature of the basin, that is, of the earth -that supports it.</p> - -<p class='c007'>The great oceans however cannot be regarded as -simple basins of water such as this. The temperature -of the surface water varies only approximately -with the latitude. It is generally speaking hottest -at the equator and coldest at the poles, but surface -currents in the intermediate regions produce many -irregularities in the surface temperature.</p> - -<p class='c007'>Again, although we have no means of knowing -what the temperature of the earth is at 1,000 fathoms -below the surface of the ocean, it is very probable -that in the great oceans the temperature of the -deepest stratum of water is considerably lower than -the true earth temperature. This is due to currents of -cold water constantly flowing from the poles towards -the equator. If these polar currents were at any time -to cease, the temperature of the lowest strata of water -would rise.</p> - -<p class='c007'>Although the polar currents cannot be actually -demonstrated nor their exact rapidity be accurately -<span class='pageno' id='Page_31'>31</span>determined, the deduction from the known facts of -physical geography that they do actually exist is -perfectly sound and beyond dispute. A few considerations -will, I think, make this clear.</p> - -<p class='c007'>If the ocean were a simple basin somewhat deeper -at the equator than at the poles, the cold water at -the poles would gradually sink down the slopes of -the basin towards the latitude of the equator, and -the bottom temperature of the water would be -constant all the world over.</p> - -<p class='c007'>A few hills here and there would not affect the -general statement that for a constant depth the temperature -of the lowest stratum of water would be -constant.</p> - -<p class='c007'>But in some places ridges occur stretching across -the oceans from continent to continent, and these -ridges shut off the cold water at the bottom of the -sea on the polar side from reaching the bottom of -the sea on the equator side.</p> - -<p class='c007'>If <span class='fss'>A</span> (fig. <a href='#fig1'>1</a>) represents a ridge stretching from -continent to continent across an ocean, and the arrow -represents the direction of the current, then the water -that flows across the ridge from the polar side to the -equator side will be drawn from the layers of water -lying above the level of the ridge, and consequently -<span class='pageno' id='Page_32'>32</span>none of the coldest water will ever get across it, -and from the level of the ridge to the bottom of the -sea on the equatorial side the water will have the -same temperature as the water at the level of the -ridge on the polar side.</p> - -<p class='c007'>It follows from this that in places where there are -deep holes in the bed of the ocean surrounded on all -sides by considerable elevations, the temperature of -the water at the bottom will be the same as the -temperature of the water on the summit of the -lowest ridges that surround them.</p> - -<div class='figcenter id001'> -<img src='images/fig_001.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 1<a id='fig1'></a>.</span>—Diagram illustrating the passage of an ocean current across a barrier (<span class='fss'>A</span>).</p> -</div> -</div> - -<p class='c007'>This explains why it is that we find that the bottom -temperature for a given depth is frequently less in -one place than it is in another, even in places of the -same parallel of latitude. One or two examples may -be taken to illustrate these points. The temperature -off Rio Janeiro in lat. 20° S. was found by the -<span class='pageno' id='Page_33'>33</span>‘Challenger’ to be 0·6° C. at a depth of 2,150 fathoms. -In a similar latitude north of the equator at a depth of -2,900 fathoms the temperature was found to be 2·2° C., -and at a point near Porto Rico there is a deep hole of -4,561 fathoms with a bottom temperature of 2·2° C.</p> - -<p class='c007'>Again it has been shown by the American expedition -that the temperature of the water at the -deepest point in the Gulf of Mexico, 2,119 fathoms, -is the same as that of the bottom of the Straits of -Yucatan, 1,127 fathoms, namely 4·1° C. And, passing -to another part of the world altogether, we find in the -small but deep sea that lies between the Philippines -and Borneo that, at a depth of 2,550 fathoms, the -temperature is 10·2° C.</p> - -<p class='c007'>These facts then show that, although at the -bottom of the deep seas the water is always very -cold, the degree of coldness is by no means constant -in the same latitude for the same depth.</p> - -<p class='c007'>We must now return to the polar currents. We -have assumed above that these currents do exist, and -it is probable that by this time the reader must have -seen why they are assumed to exist.</p> - -<p class='c007'>The water at the bottom of the ocean is exceedingly -cold. Where does this coldness come from? -It is obvious that in temperate and tropical climes -<span class='pageno' id='Page_34'>34</span>it does not come from the surface. Nor is it at all -probable that it comes from the earth upon which -the water rests; for, if it were so, the temperature for -water of a given depth would always be the same. -We should not find the bottom temperature of 0·4° C. -at 2,900 fathoms off Rio de la Plata and a temperature -of 2·2° F. in 4,561 fathoms off Porto Rico.</p> - -<p class='c007'>In fact the only hypothesis that can with any -show of reason be put forward to account for the -temperature of the bottom of the ocean is that which -derives its coldness from the Polar ice.</p> - -<p class='c007'>We have at present very little evidence to enable -us to judge of the force and direction of the polar -currents in the two hemispheres, but the researches of -the ‘Challenger’ prove almost conclusively that in the -Atlantic Ocean there is a very strong predominance -of the Antarctic polar current. In fact it seems very -probable that the Arctic polar current, if it exist at -all, is very small and confined to the eastern and -western shores of the North Atlantic.</p> - -<p class='c007'>It is very probable, however, that these currents -at the bottom of the ocean are extremely slow, -and, as the water is never affected by tides or storms, -the general character of the deep sea is probably -one of calm repose. This is a matter of no little -<span class='pageno' id='Page_35'>35</span>importance; for, in the consideration of the characters -presented by the fauna of any particular region, it is -always necessary to take into account the physical -difficulties the animals have to contend against and -the modifications of structure they present to combat -these difficulties.</p> - -<p class='c007'>Thus in a region such as that presented by the -deep sea, where there are no rapid tides, we should -not expect to find such a powerful set of body -muscles in the free-swimming forms nor such a firm -vertebral column as in the animals that live in -more lively water.</p> - -<p class='c007'>Perhaps it is of the nature of an assumption to -say that there are no rapid currents and tides in the -abysmal depths of the ocean, for we have no means of -demonstrating or even of calculating the rate of flow of -these waters. But it is a reasonable hypothesis and -one that we may well use until the contrary is proved.</p> - -<p class='c007'>A fact of some importance that supports this -hypothesis, as regards some parts of the ocean at -least, is presented by the sea-anemones.</p> - -<p class='c007'>Many of the shallow-water Actinians are known -to possess minute slits in the tentacles and disc, -affording a free communication between the general -body cavity or cœlenteron and the exterior.</p> - -<p class='c007'><span class='pageno' id='Page_36'>36</span>In many deep-sea forms the tentacles are considerably -shorter and the apertures larger than they are -in shallow-water forms. It is difficult to believe that -such forms, perforated by, comparatively speaking, -large holes, could manage to live in rapidly flowing -water, for if they did so they would soon be smothered -by the fine mud that composes the floor of all the deep -seas. In fact anemones of the type presented by such -forms as <i>Sicyonis crassa</i> are only fitted for existence -in sluggish or still water.</p> - -<div class='figcenter id003'> -<img src='images/fig_002.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 2<a id='fig2'></a>.</span>—<i>Sicyonis crassa.</i> <span class='fss'>M</span>, mouth; <span class='fss'>S</span>, ciliated groove; <span class='fss'>T</span>, tentacles. Each tentacle is perforated by a single large aperture. (After Hertwig.)</p> -</div> -</div> - -<p class='c007'>Another character that must be taken into consideration -<span class='pageno' id='Page_37'>37</span>is that presented by the floor of the great -oceans. The floor of the ocean, if it were laid bare, -would probably present a vast undulating plain of -fine mud. Not a rock, not even a stone would be -visible for miles.</p> - -<p class='c007'>The mud varies in different parts of the globe -according to the depth, the proximity to land, the -presence of neighbouring volcanoes or the mouths of -great rivers.</p> - -<p class='c007'>The Globigerina ooze is perhaps the best known -of all the different deep-sea deposits. It was discovered -and first described by the officers of the American -Coast Survey in 1853. It is found in great -abundance in the Atlantic Ocean in regions shallower -than 2,200 fathoms. Deeper than this, it gradually -merges into the ‘Red mud.’ It is mainly composed of -the shells of Foraminifera, and of these the different -species of Globigerina are the most abundant. It is -probably formed partly by the shells of the dead -Foraminifera that actually live on the bottom of the -ocean and partly by the shells of those that live near -the surface or in intermediate depths and fall to the -bottom when their lives are done.</p> - -<p class='c007'>So abundant are the shells of these Protozoa that -nearly 95 per cent. of the Globigerina ooze is composed -<span class='pageno' id='Page_38'>38</span>of carbonate of lime. The remaining five per -cent. is composed of sulphate and phosphate of lime, -carbonate of ammonia, the oxides of iron and -manganese, and argillaceous matters. The oxides of -iron and manganese are probably of meteoric origin; -the argillaceous matter may be due to the trituration -of lumps of pumice stone and to the deposits caused -by dust storms.</p> - -<div class='figcenter id001'> -<img src='images/fig_003.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 3<a id='fig3'></a>.</span>—Globigerina ooze. (After Agassiz.)</p> -</div> -</div> - -<p class='c007'>Globigerina ooze may be found on the floor of -the ocean at depths ranging from 500 to 2,800 -fathoms of water in equatorial and temperate latitudes. -The reason that it is not found in Arctic -seas may be that the cold surface waters of these -regions do not bear such an abundant fauna of Foraminifera. -<span class='pageno' id='Page_39'>39</span>This is supported by the fact that it -extends ten degrees further north than south in the -Atlantic, the warm water of the Gulf Stream bearing -a richer fauna than the waters of a corresponding -degree of latitude in the Southern Sea.</p> - -<p class='c007'>The Pteropod ooze has only twenty-five per cent. -of carbonate of lime. It contains numerous shells -of various Pteropods, Heteropods, and Foraminifera, -but nearly fifty per cent. of its substance is composed -of the siliceous skeletons of Radiolaria and the -frustules of diatoms.</p> - -<p class='c007'>According to Murray it is found in tropical -and subtropical seas at depths of less than 1,500 -fathoms.</p> - -<p class='c007'>The Radiolarian ooze is found only in the deepest -waters of the Central and Western Pacific Ocean. In -some of the typical examples, not a trace of carbonate -of lime was to be found, but in somewhat shallower -waters a few small fragments occurred.</p> - -<p class='c007'>A Diatom ooze, mainly composed of the skeletons -of diatoms, has also been found in deep water near the -Antarctic Circle, but it has not apparently a very wide -range.</p> - -<p class='c007'>Of all the deep-sea deposits, however, the so-called -‘Red mud’ has by far the widest distribution. -<span class='pageno' id='Page_40'>40</span>It is supposed to extend over one-third of the earth’s -surface. It is essentially a deep-sea deposit, and one -that is found in its typical condition at some considerable -distance from continental land. Like the -Globigerina ooze it is never found in enclosed seas. -To the touch it is plastic and greasy when fresh, but -it soon hardens into solid masses. When examined -with the microscope it is seen to be composed of extremely -minute fragments rarely exceeding 0·05 mm. -in diameter. It contains a large amount of free silica that is probably formed by the destruction of numerous -siliceous skeletons, and a small proportion of silicate -of alumina. It usually contains the remains of -diatoms, radiolaria, and sponge spicules, and occasionally -lumps of pumice stone, meteoric nodules, and, in -colder regions, stones and other materials dropped -by passing icebergs.</p> - -<p class='c007'>In the great oceans, then, we find in the deepest -places red mud, or, where there is an abundant Radiolarian -surface fauna, Radiolarian ooze; in water that -is not deeper than about 2,000 fathoms, we find the -Globigerina ooze; in shallower waters and in some -localities only Pteropod ooze.</p> - -<p class='c007'>It must not be supposed that sharp limits can -anywhere be drawn between these different kinds of -<span class='pageno' id='Page_41'>41</span>deposits, for they pass gradually into one another and -present many intermediate forms.</p> - -<p class='c007'>It is probable that the sea water by virtue of the -free carbonic acid it contains in solution is able to -exert a solvent action upon the calcium carbonate -shells of animals as they sink to the bottom, and -during the long and very slow journey from the surface -to the bottom of the deepest seas these shells are -completely dissolved.</p> - -<p class='c007'>The first to be dissolved would be the thin -delicate shells of the Pteropods and Heteropods, for -besides the fact that they present a wider surface to -the solvent action of the water they are probably influenced -more by tide and currents, sink more slowly -and erratically, and thus have a longer journey to -perform.</p> - -<p class='c007'>Then the smaller but more solid and compact -shells of the Foraminifera are dissolved, and lastly, in -the deepest water only the siliceous skeletons of the -radiolaria and diatoms are able to reach their last -resting place at the bottom of the ocean.</p> - -<p class='c007'>These four oozes then are characteristic of the -floor of the deep oceans. In the proximity of land -and in inland seas where deep water occurs, other -muds are found differing from one another in accordance -<span class='pageno' id='Page_42'>42</span>with the character of the coasts in their vicinity. -It is not necessary to give a detailed account of them, -but a few remarks on some of the more pronounced -forms may not be without interest.</p> - -<p class='c007'>The blue mud contains eighty per cent. of a mixture -of quartz, mica, felspar, hornblende, and other -minerals, mixed with a considerable quantity of decomposing -animal and vegetable substance, the calcareous -remains of foraminifera, mollusca, worms, -echinoderms, alcyonaria and corals, and the siliceous -skeletons of radiolaria and diatoms.</p> - -<p class='c007'>The green mud is characterised by a large percentage -of glauconite.</p> - -<p class='c007'>The red muds characteristic of the Brazilian -coast contain a large amount of ochreous matter -brought into the sea by the great rivers.</p> - -<p class='c007'>In the neighbourhood of active volcanoes there is -a characteristic volcanic mud, and in the coral seas -the deep-sea deposits contain a large percentage of -the calcareous remains of dead corals.</p> - -<p class='c007'>One more character of the deep-sea region must -be referred to before we pass on, and that is the -absence of vegetable life. It has not been determined -yet with any degree of accuracy where we are to -place the limit of vegetable life, but it seems probable -<span class='pageno' id='Page_43'>43</span>that below a hundred fathoms no organisms, excepting -a few parasitic fungi, are to be found that can be -included in the vegetable kingdom. While then the -researches of recent times have proved beyond a doubt -that there is no depth of the ocean that can be called -azoic, they have but confirmed the perfectly just -beliefs of the older naturalists that there is a limit -where vegetable life becomes extinct. It is not difficult -to see the reason for this. All plants, except a -few parasites and saprophytes, are dependent upon -the influence of direct sunlight, and as it has been -shown above that the sunlight cannot penetrate -more than a few hundred fathoms of sea water, -it is impossible for plants to live below that -depth.</p> - -<p class='c007'>The absence of vegetable life is an important -point in the consideration of the abysmal fauna, for -it is in consequence necessary to bear in mind that -the food of deep-sea animals must be derived from -the surface. It is possible that deep-sea fish, in -some cases, feed upon one another and upon deep-sea -crustacea, that deep-sea crustacea feed upon deep-sea -worms, that deep-sea echinoderms feed upon deep-sea -foraminifera, and so on through all the different -combinations; but the fauna would soon become -<span class='pageno' id='Page_44'>44</span>exhausted if it had no other source of food supply. -This other source of food supply is derived from the -bodies of pelagic organisms that fall from the upper -waters of the ocean, and is composed of protozoa, -floating tunicates, crustacea, fish, and other animals, -together with diatoms and fragments of sea-weed.</p> - -<div class='chapter'> - <span class='pageno' id='Page_45'>45</span> - <h2 class='c005'>CHAPTER III<br /> <span class='large'>THE RELATIONS OF THE ABYSMAL ZONE AND THE ORIGIN OF ITS FAUNA</span></h2> -</div> - -<p class='c006'>In the study of the geographical distribution of -terrestrial animals one of the great difficulties met -with is the impossibility of defining exactly the -limits of the regions into which we divide the surface -of the earth. In a general way we recognise that -there is an Australian region, an Ethiopian region, -&c.; but, when we come to discuss the exact position -of the frontier lines that separate these regions -from their neighbours, we find all kinds of difficulties -to overcome and inconsistencies to meet.</p> - -<p class='c007'>For the sake of convenience it is useful to adopt -certain arbitrary limits for these regions, notwithstanding -these difficulties and inconsistencies, but we -must recognise the fact that nature recognises no -such limits, that every region overlaps its neighbours -to a greater or less extent, and that there are many -<span class='pageno' id='Page_46'>46</span>debateable grounds in the world where the fauna -characteristic of one region is mixed with that -characteristic of another.</p> - -<p class='c007'>But this difficulty in defining the exact limits -of the terrestrial faunistic regions is even more pronounced -in the case of the regions and zones of the -marine fauna.</p> - -<p class='c007'>On the dry land we find mountain ranges, forests, -deserts, and other barriers, that to a very considerable -extent prevent the mixing of one fauna with another, -but in the sea there are no barriers of anything like -the same importance, but one fauna gradually merges -into the neighbouring fauna according to the temperature, -the pressure, the amount of light, the salinity -of the water or the food supply. This then is one of -the difficulties met with in the study of the geographical -distribution of the marine fauna.</p> - -<p class='c007'>But there is another that leads to almost greater -complications. In considering terrestrial life it is -customary to refer only to regions of geographical, -or perhaps it would be more correct to call it—superficial -distribution. It would be quite possible, -however, to subdivide the geographical areas into -zones of elevation above the sea-level, not very -clearly marked off from one another, it is true, but -<span class='pageno' id='Page_47'>47</span>nevertheless each showing a number of characteristic -features. This idea is expressed, for example, when -we speak of the Alpine fauna, the Himalayan fauna, -or the fauna of the great Andes.</p> - -<p class='c007'>In the study of the marine fauna and flora we -must notice, it is the depth of the water, or in other -words the depression of the habitats below the sea-level, -that forms the most important consideration. -Geographical sub-regions may be recognised and -defined with a certain amount of accuracy, especially -in the case of the fauna of the shallow waters, but by far -the most important changes in the general characters -of the fauna are found when we pass from one ‘zone’ -of depression to another. Thus in describing any -particular marine fauna we should mention first of -all its zone or sub-zone of depression and then its -geographical region and sub-region. For example, -we may speak of the fauna of the pelagic zone of -the British sub-region of the European region, or the -fauna of the abysmal zone of the Northern sub-region -of the Atlantic region.</p> - -<p class='c007'>We can recognise three primary zones of the -marine fauna which we may call the ‘Pelagic,’ the -‘Neritic,’ and the ‘Abysmal’ zones.</p> - -<p class='c007'>The Pelagic zone includes the superficial waters -<span class='pageno' id='Page_48'>48</span>of all seas extending from the surface to a depth -which cannot at present be very accurately determined, -but is probably the same as the limit of the influence -of direct sunlight.</p> - -<p class='c007'>The animals of this zone are frequently characterised -by a general transparency of their tissues, -a white or sea water (i.e. blue or green) colour, -an organisation capable of prolonged swimming or -floating movement, and by giving birth to floating -eggs which hatch out transparent larvæ or embryos.</p> - -<p class='c007'>The pelagic zone may be divided into several -geographical regions and sub-regions, which it would -be beyond the scope of this book to enumerate here, -but there is one that calls for a few brief remarks. In -many parts of the ocean there may be found vast -areas of floating sea-weed, which carry with them a -population of crustacea and other animals peculiarly -their own. This ‘sargasso’ fauna presents so many -characteristics and so many features different from -that of the ordinary pelagic fauna, that the tracts of -sea bearing this weed must be considered to rank as -a special region of the pelagic zone, which may be -called the Sargasso region.</p> - -<p class='c007'>The zone of shallow water for which we shall adopt -Professor Haeckel’s term—the Neritic zone—embraces -<span class='pageno' id='Page_49'>49</span>all parts of the seas of less depth than 500 fathoms, -including the inland seas, the shores of great continents -and islands, and the shallow banks in the -great oceans. It does not include the superficial -waters—which belong to the pelagic zone—but extends -only from the actual bottom to a distance of -a few fathoms above it. The fauna of this zone is -extremely varied, consisting of animals that swim, -crawl, or are permanently fixed to the bottom, -animals of almost every variety of colour and marking, -and of every size and shape.</p> - -<p class='c007'>The exact limits of the Neritic sub-zones are not -easy to define. The distinguished naturalist Forbes, -to whom the abysmal zone was unknown, divided -the seas from 0–50 fathoms in depth into three zones—the -littoral zone lying between tide-marks, the -laminarian zone extending from 0–15 fathoms, and -the coralline zone from 15–50 fathoms.</p> - -<p class='c007'>The first of these will stand as a sub-zone, the -animals that are able to withstand exposure to the -sun and air either in pools or upon the rocks and -sand even for a few minutes frequently possessing -features that distinguish them from those dwelling -beyond low-water mark, just as those more active -creatures that migrate backwards and forwards with -<span class='pageno' id='Page_50'>50</span>the ebb and flow of every tide differ from the -dwellers in the open sea. There is, it is true, at -every low tide, a migration of part of the fauna -of this sub-zone into the next, but still it is sufficiently -well defined to be allowed to remain in -our category.</p> - -<p class='c007'>The second sub-zone is not so easy to define. -The terms ‘laminarian’ and ‘coralline’ used by -Forbes are only applicable to certain geographical -regions and must be abandoned for general use.</p> - -<p class='c007'>We can only recognise one sub-zone between the -littoral sub-zone and the abysmal zone, for notwithstanding -the important varieties it exhibits in the -nature of the bottom, whether it be rocky, sandy, or -weedy, the amount of light, the temperature of the -water, and the rapidity of the currents, it is not -possible at present to point to any general characters -of the fauna of its different parts to justify us in -subdividing it.</p> - -<p class='c007'>The name that may be given to this second sub-zone -of the neritic zone is the Katantic—the sub-zone -of the slopes.</p> - -<p class='c007'>The last well-marked zone is the abysmal, extending -from the 500–fathom line to the greatest -depths of the ocean, one of enormous superficial area, -<span class='pageno' id='Page_51'>51</span>one that it is most difficult to investigate, and one -about which we know but little.</p> - -<p class='c007'>In the present state of our knowledge we cannot -divide it into any well-marked sub-zones nor even into -geographical regions or sub-regions. It is not divided -into sections by any important geographical barriers, -and the general characters presented by its fauna are -practically the same all the world over.</p> - -<p class='c007'>Professor A. Agassiz has pointed out in his -‘Challenger’ monograph that the deep-sea echinoids -of the Atlantic Ocean differ from those living in -corresponding depths in the Pacific Ocean, but it is -doubtful whether any such well-marked differences -can be observed in other groups of animals. If, in -the course of time, increased knowledge of deep-sea -animals emphasises the difference between the -abysmal fauna of the Pacific and that of the Atlantic, -then we can divide this zone into two geographical -regions; but at present it seems more correct to -consider the abysmal zone as one that is indivisible -either bathymetrically or geographically.</p> - -<p class='c007'>Before passing on to the consideration of the -general characters of the abysmal fauna, there are -still one or two points that must be just briefly -referred to.</p> - -<p class='c007'><span class='pageno' id='Page_52'>52</span>It is the function of every true naturalist to consider -animals from every possible point of view. Not -only must he regard them as members of a certain -species belonging to a genus, a family, an order, and -so on, presenting certain peculiarities of structure -and development; not only must he regard them as -inhabitants of a certain locality or zone of depth, but -he must also pay attention to their habits and mode -of life.</p> - -<p class='c007'>Now amongst marine animals we can recognise -three principal modes of life. Some animals simply -float or drift about with the currents of the sea and -are unable to determine for themselves, excepting, -perhaps, within very small limits, the direction in -which they travel. Such are the countless forms of -protozoa, the jelly-fishes and medusæ, numerous -pelagic worms and crustacea, the pyrosomas and -salps, and many other forms well known to those -who are in the habit of using the tow-net. This -portion of the fauna has recently been called the -Plankton.</p> - -<p class='c007'>Then there are the animals that are capable of -very considerable swimming movements, animals -that are able to stem the tide and migrate at will -from one part of the sea to another, such as the -<span class='pageno' id='Page_53'>53</span>cetacea, most fishes, and perhaps also many cephalopods. -This portion of the fauna has been called the -Nekton.</p> - -<p class='c007'>And lastly we have those animals that remain -perfectly fixed to the bottom or are capable only -of creeping or crawling over the rocks and sand, -such as the sponges, hydroids, sedentary tunicates, -gasteropods, most lamellibranchs, and many crustacea. -This portion of the fauna has been called the -Benthos.</p> - -<p class='c007'>Although it will not be necessary to use these -terms very frequently in this little book, it may be -advisable for the reader to bear in mind that in any -exhaustive treatise on the marine fauna such terms -would be employed, and that in the chapters dealing -with the fauna of the abysmal zone we should find -accounts of the ‘bathybial plankton,’ the ‘bathybial -nekton,’ and the ‘bathybial benthos.’</p> - -<p class='c007'>Lastly we must consider quite briefly the views -that have been held concerning the origin of the -abysmal fauna.</p> - -<p class='c007'>As soon as it became clear to naturalists that -there is no part of the ocean, however deep it may -be, that deserves the name ‘azoic,’ but that almost -every part has a fauna of greater or less density, -<span class='pageno' id='Page_54'>54</span>the problem of the origin of this fauna presented -itself.</p> - -<p class='c007'>Whence came the curious creatures that live -mostly in total darkness and can sustain without -injury to their delicate and complicated organisation -the enormous pressure of the great depths? Are -they the remnants of the fauna of shallow prehistoric -seas that have reached their present position by the -gradual sinking of the ocean basins? Or, are we to -look upon the abysmal region as the nursery of -the marine fauna, the place whence the population -of the shallow waters was derived? Neither of these -answers is supported by the facts with which we -are now well acquainted. The fauna of the abysmal -region does not show a close resemblance to that of -any of the past epochs as revealed to us by geology, -nor are we justified in assuming without much -stronger evidence than we now possess, that the -oceans have undergone any such great depression as -this first theory presupposes.</p> - -<p class='c007'>Nor can we consider for a moment that the abyss -was the original source of the shallow-water fauna; -for not only do we find but few types that can be -considered to be, in any sense of the word, ancestral -in character; but on the contrary most of the animals -<span class='pageno' id='Page_55'>55</span>of the deep sea seem to be specially modified types of -shallow-water forms. The most probable explanation -of the origin of the deep-sea fauna is the one that was -put forward by Moseley and has been since supported -by almost every authority on the subject, namely, that -the fauna of the deep sea has been derived from successive -immigrations of the animals from the shallow -water.</p> - -<p class='c007'>This view is supported by the fact that the deep-sea -fauna is much richer in the neighbourhood of land -than it is in regions more remote from it. Many -examples could be given to illustrate this point. -The extraordinary richness of the deep-sea fauna on -the western slopes of the floor of the Atlantic has -been frequently commented on by the naturalists connected -with the expeditions of the American vessels, -the ‘Blake,’ the ‘Fish Hawk,’ and the ‘Albatross.’ -Moseley called attention several years ago to a few -localities in the neighbourhood of the land especially -rich in deep-sea forms in comparatively shallow -waters, such as one near the island of Sombrero in -the Danish West Indies, where within sight of the -lighthouse a haul of the dredge in 450 fathoms brought -up a rich fauna of blind crustacea, corals, echinoderms, -sponges, &c. Another off Kermadec in 630 -<span class='pageno' id='Page_56'>56</span>fathoms brought up numerous curious blind fishes, -ascidians, cuttlefishes, crustacea, <i>Pentacrinus</i>, and -large vitreous sponges, and there are similar localities -lying between Aru and Ke and between the -Nanusa archipelago and the Talaut islands. The -deep water off the Norwegian, Scotch, Irish, and -Portuguese coasts also seems to be particularly rich -in various forms of animal life. The same is probably -true of the deep sea of many other regions -in the neighbourhood of land, and, although it -cannot be taken to be a rule without exceptions—the -abysmal fauna off the western coasts of the -Panama region being, according to the recent -researches of Alexander Agassiz in the ‘Albatross,’ -particularly poor—yet we can assert as a statement -of very general application that the further removed -from continental land, the poorer is the abysmal -fauna.</p> - -<p class='c007'>Another argument that has been brought forward -by Moseley in support of his view is that there is a -certain relationship between the deep-sea fauna of -any particular region and the shallow-water fauna of -the nearest coasts. This is a point that is not easy -to illustrate by examples, but as Moseley’s argument -has not, so far as I am aware, been disputed by any -<span class='pageno' id='Page_57'>57</span>of the naturalists who have followed him in this line -of work, and the recent results of the ‘Albatross’ in -comparing the deep-sea fauna of the eastern and -western sides of the isthmus of Panama seem if anything -to support it, we can take it as a point in -favour of his view of the origin of the abysmal fauna.</p> - -<p class='c007'>It is impossible to say at present at what time in -the world’s history these migrations commenced, but, -as Agassiz points out, none of the palæozoic forms -are found in the deep sea, and this seems to indicate -that the fauna did not commence its existence earlier -than the cretaceous period.</p> - -<p class='c007'>It is quite possible, however, that part of the fauna -of the deep sea has been derived directly from the -pelagic zone. The occurrence of bathybial Radiolaria, -Foraminifera and Siphonophora, and among fishes -genera and species of the pelagic families Sternoptychidæ -and Scopelidæ, suggest that this zone may have -contributed very largely to the fauna of the abyss.</p> - -<p class='c007'>Much of course still remains to be done before -we can consider any of these interesting problems -connected with the deep-sea fauna to be definitely -solved. All we can do at present is to speculate -upon the direction in which the facts at our disposal -seem to point, and by following up one clue after -<span class='pageno' id='Page_58'>58</span>another hope that we may eventually arrive at the -truth. The task may be a difficult one, but it will -reward our efforts. If truth is hard to find when -it lies at the bottom of a well, how much more -inaccessible must it be when it lies hidden in the -darkness of the sea’s abyss!</p> - -<div class='chapter'> - <span class='pageno' id='Page_59'>59</span> - <h2 class='c005'>CHAPTER IV<br /> <span class='large'>THE CHARACTERS OF THE DEEP-SEA FAUNA</span></h2> -</div> - -<p class='c006'>The general characters presented by animals living -in deep water may be considered under several -headings. The most important are those that are -directly or indirectly related to the fact that the -animals live either in total darkness or in the faint -and probably intermittent light emitted by phosphorescent -animals; namely, the colour of the skin -and the peculiarities of the eyes.</p> - -<p class='c007'>The colours of the skin of the deep-sea animals -vary to a very remarkable extent in the different -groups. It cannot be said that there is any one -colour at all predominant, and it is only in certain -classes that black, white, or dull-coloured animals are -more numerous than others. The colours are however -usually very evenly distributed, and we find but -few examples of animals with spots, stripes, or other -pronounced markings.</p> - -<p class='c007'>The majority of the fish are dark brown or black, -but many other colours are represented. Thus -<span class='pageno' id='Page_60'>60</span><i>Ipnops Murrayi</i>, a typical deep-sea fish, is yellowish -brown with colourless fins, and it exhibits a further -character not uncommon in these abysmal forms, -namely black buccal and branchial cavities. <i>Typhlonus -nasus</i>, again, is said to be of a light brownish -colour, with black fins. Many other examples -could be given to show the prevalence in these -regions of these black, dull, and pale uniform colours. -But there are many exceptional cases. <i>Neoscopelus -macrolepidotus</i>, for example—a form that according to -Günther undoubtedly belongs to the bathybial region—is -distinguished by its brilliant colours. It is bright -red mixed with azure blue, the whole relieved by -silver spots with circles of black on the abdomen.</p> - -<p class='c007'><i>Prorogadus nudus</i> is of a pale rose colour, with the -under and lateral sides of the head bluish black.</p> - -<p class='c007'><i>Rhodichthys regina</i>, found in 1,280 fathoms of -water, is uniformly bright red in colour.</p> - -<p class='c007'>A. Agassiz says in his reports on the dredging -operations on the west coast of America: ‘The -coloration of the deep-sea fishes is comparatively -monotonous. The tints are all a light violet base, -tending more or less to brownish or brownish yellow, -or even to a greenish tint, especially among the -Macruridæ. Some of the Liparidæ were of a dark -<span class='pageno' id='Page_61'>61</span>violet, and one species was characterised by a brilliant -blue band. The Ophidiidæ, <i>Nemichthys</i>, and the like, -are usually of an ashy violet tint, while in <i>Ipnops</i> -and <i>Bathypterois</i> the tints were of a decidedly -yellowish brown.’</p> - -<p class='c007'>That the deep-sea fish are usually devoid of any -pronounced spots, stripes, and other markings, is now -well recognised. It may not be altogether out of place, -however, to refer briefly to a few exceptions.</p> - -<p class='c007'>The black circles on the abdomen of <i>Neoscopelus -macrolepidotus</i> have already been referred to.</p> - -<p class='c007'><i>Halosaurus johnsonianus</i>, has a black spot on the -tail.</p> - -<p class='c007'><i>Aulostoma longipes</i> has three pairs of large black -spots on the ventral side, but the specimen taken -in 1,163 metres of water by the ‘Talisman’ was -probably a young one.</p> - -<p class='c007'>It is very probable that in all the exceptional -cases, when fish taken in deep-sea water have exhibited -such spots and markings, they are examples either -of fish that have quite recently adopted an abysmal -habitat or of young specimens exhibiting ancestral -inherited characters.</p> - -<p class='c007'>In referring to a specimen of <i>Raja circularis</i>, taken -by the ‘Triton’ in 516 fathoms, Günther says: ‘It is -<span class='pageno' id='Page_62'>62</span>notable that the spot on each side of the back which -in littoral specimens is variegated with yellow is -much smaller in the deep-sea specimen and uniformly -black without yellow.’</p> - -<p class='c007'>It seems to be then a very general rule among -fishes that as they migrate into deeper water the -spots and stripes, so conspicuous among many forms -living on the surface and in shallow water, disappear, -and the coloration of the body becomes more evenly -distributed and uniform.</p> - -<p class='c007'>Among the Mollusca, the deep-sea Cephalopods -seem to be usually violet, but an <i>Opisthoteuthis Agassizii</i> -caught by the ‘Blake’ is stated to be of a dark -chocolate colour, a <i>Nectoteuthis Pourtalesii</i> reddish-brown, -and a <i>Mastigoteuthis</i> orange brown, while of -the specimens brought home by the ‘Challenger,’ -<i>Cirroteuthis magna</i> was said to be ‘rose’ when captured, -and the spirit specimens of <i>Cirroteuthis pacifica</i> -and <i>Bathyteuthis abyssicola</i> were purplish madder -and purplish brown respectively.</p> - -<p class='c007'>The shells of the Gasteropods and Lamellibranchs -living in the abyss are frequently so thin as to be -almost transparent, and are, with very few exceptions, -white or pale straw coloured. The colour of the -only specimen of nudibranchiate Mollusca that has -<span class='pageno' id='Page_63'>63</span>been found in the abysmal zone, namely, <i>Bathydoris -abyssorum</i>, is described by Mr. Murray as follows: -‘The body of the living animal was gelatinous and -transparent, the tentacles brown, the gills and protruding -external generative organ orange, the foot -dark purple.’</p> - -<p class='c007'>Among the Crustacea various shades of red are -the prevailing colours. ‘The deep-sea types, like -<i>Gnathophausia</i>, <i>Notostomus</i>, and <i>Glyphocrangon</i>,’ says -Agassiz, ‘are of a brilliant scarlet; in some types, as -in the Munidæ and Willemoesiæ, the coloration tends -to pinkish or yellowish pink, while in <i>Nephrops</i> and -<i>Heterocarpus</i> the scarlet passes more into greenish -tints and patches.’<a id='r1' /><a href='#f1' class='c013'><sup>[1]</sup></a> But perhaps the most remarkable -point in the colour of the crustacea is that which -immediately follows the paragraph I have just quoted. -‘The large eggs of some of the deep-sea genera are -of a brilliant light blue, and in one genus of Macrura -we found a dark metallic blue patch on the dorsal -part of the carapace in marked contrast to the brilliant -crimson of the rest of the body.’</p> - -<div class='footnote' id='f1'> -<p class='c007'><a href='#r1'>1</a>. In the recent researches of the ‘Investigator’ a few crustacea -of rather exceptional colour were found. Whilst the great -majority of them are described to be pink or red in colour when -alive, <i>Gnathophausia bengalensis</i> is deep purple lake, <i>Haliporus -neptunus</i> lurid orange, and <i>Aristaeus coruscans</i> bright orange.</p> -</div> - -<p class='c007'><span class='pageno' id='Page_64'>64</span>The occurrence of this blue colour in Crustaceans -of the deep sea is very remarkable, for blue is a colour, -as Moseley pointed out many years ago, that is rarely -met with in the fauna of the abyss, and it is certainly -very exceptional in the crustacea of that zone.</p> - -<p class='c007'>Among the deep-sea Echinoderma we find a -wonderful variety of coloration. Moseley says that -many deep-sea Holothurians, for example, are deep -purple, and Agassiz reports that in one species the -colour was of a delicate green tinge. ‘We obtained,’ -he adds, ‘a white <i>Cucumaria</i> and some species of -<i>Benthodytes</i> of the same colour,’ while others vary -from transparent milky white to yellow and light -yellowish brown and even pinkish colours. The -Crinoids are described by the authorities to be white, -purple, yellow and brownish-chestnut, and of the -other groups of the echinoderms we read that the -star-fishes are, as a rule, of duller colours than the -crustacea, but all more or less pink or red. ‘The -Hymenasteridæ, on the contrary, vary from light -bluish violet to deep reddish chestnut colours.’ The -brittle stars are red and orange or dullish grey, -while the urchins may be deep violet, claret coloured, -brownish, or of a delicate pink.</p> - -<p class='c007'>It is impossible to account for this extraordinary -<span class='pageno' id='Page_65'>65</span>variety of colour in the deep-sea echinoderms. It is -hardly probable that it can be protective or warning in -function, and it is difficult to suppose that it is due -to any peculiar excretory process. Whether it is due -in any way to the influence of the environment, or, -like the colour of autumn leaves, to the chemical -degeneration of colours that in the shallow-water -ancestry were functional, are problems that must be -left for the future to decide.</p> - -<p class='c007'>The colour of the deep-sea Cœlenterates has unfortunately -not been recorded in all cases, but still -the few observations that we have show that in this -group, as in the last, almost every tint and shade -are represented.</p> - -<p class='c007'>The colouring of the deep-sea jelly-fishes is said -to be usually deep violet or yellowish red. However -‘a species of <i>Stomobrachium</i>,’ says Agassiz, ‘is remarkable -for its light carmine colour, a tint hitherto -not observed among Acalephs.’</p> - -<p class='c007'>Moseley records most minutely the colour of some -of the deep-sea anemones and corals, and calls attention -to the very general presence of madder brown -in the soft parts. Agassiz says: ‘Among deep-sea -Actiniæ, a species of a new <i>Cereanthus</i> was of -a dark brick-red, while other actinians allied to -<span class='pageno' id='Page_66'>66</span><i>Bunodes</i> were of a deep violet. Actinauge-like forms -with tentacles of a pinkish-violet tinge frequently -have the column of a yellow shade. The Zoanthidæ -were greyish-green.’ And again, in his narrative of -the voyage of the ‘Blake,’ he records that ‘some of -the deep-sea corals are scarlet, deep flesh-coloured, -pinkish orange, and of other colours,’ and in referring -to the Gorgonian <i>Iridogorgia</i> he says: ‘The species -are remarkable for their elegance of form and for the -brilliant lustre and iridescent colours of the axis, in -some of a bright emerald green, in others like burnished -gold or mother-of-pearl.’</p> - -<p class='c007'>The fauna of the deep sea then, taken as a whole, -is not characterised by the predominance of any one -colour. The shades of red occur rather more frequently -than they do in the fauna of any other zone -or region, but whether this is in any way connected -with the fact that red is the complementary colour to -that of the phosphorescent light, in which many of -these animals live, it is at present difficult to say; -it is possible that, when we have further information -concerning the colours of the animals living in the -deeper parts of the Neritic zone, another explanation -may be forthcoming.</p> - -<p class='c007'>Moseley points out that there are no blue animals -<span class='pageno' id='Page_67'>67</span>known to live in deep water, and it might be added -that green is extremely rare as a colouring matter in -abysmal animals, although the phosphorescent light -given out by some of the echinoderms is green.</p> - -<p class='c007'>Blue, as a colouring matter of marine animals, -living on the surface or in shallow water, is not uncommonly -met with, distributed in the form of bands -or stripes, but green is extremely common in fishes, -crustacea and cœlenterates, and it is a point of very -considerable importance that in this respect there -is a very great difference between the deep-sea and -the shallow-sea faunas.</p> - -<p class='c007'>If a considerable collection of living abysmal forms -could be placed upon one table and a similar collection -of shallow-water forms upon another, I believe -that the first general impression upon the mind of -one who saw them both for the first time would -be the presence of green colours in the last-named -collection, and the absence of it in the other.</p> - -<p class='c007'>The eyes of the animals that live in deep-sea -water undergo curious modifications. If the fauna -of the abysmal region were confined to conditions of -absolute darkness, we should expect to find either a -total absence of eyes or mere rudiments of them only -in those forms that have recently migrated from -<span class='pageno' id='Page_68'>68</span>the shallow water. This is the case with the fauna -of the great caves. There is probably total darkness -in these underground lakes and streams, and there -is only the remotest possibility of the animals living -in them ever seeing, even temporarily, a ray of -sunlight or even a glimmer of phosphorescence -during the whole of their life-time. We find then -that the cave fauna is totally blind.</p> - -<p class='c007'>The conditions in the deep sea are not quite the -same. In some regions there is probably a very considerable -illumination by phosphorescent light, and it -is quite possible that many of the characteristic deep-sea -forms may occasionally wander into shallower -regions where faint rays of sunlight penetrate, or even -that the young stages of some species may be passed -at or near the surface of the sea. Taking these points -into consideration, then, it is not surprising to find -that, in the deep seas, there are very few animals, -belonging to families usually provided with eyes, that -are quite blind.</p> - -<p class='c007'>In the majority of cases we find that the eyes are -either very large or very small. Only in a small -minority of cases do we find that the eyes are recorded -to be moderate in size. The relation between the -large-eyed forms and the small-eyed forms is not the -<span class='pageno' id='Page_69'>69</span>same in all the regions of deep seas. In depths of -300 to 600 fathoms the majority are large-eyed forms. -This is as we should expect, for it is more than -probable that many of these forms occasionally wander -into shallower waters where there is a certain amount -of sunlight.</p> - -<p class='c007'>In depths of over 1,000 fathoms, the small-eyed -and blind forms are in a majority, although many -large-eyed forms are to be found.</p> - -<p class='c007'>Among fishes, for example, we find the species of -<i>Haloporphyrus</i> found in depths of 300–600 fathoms -with large eyes; and so with <i>Dicrolene</i>, <i>Cyttus -abbreviatus</i>, and many other forms that are known -to live in water of less depth than 700 fathoms; -while on the other hand in <i>Melanocetus Murrayi</i>, <i>Ipnops -Murrayi</i>, many deep-sea eels and other fish that are -truly abysmal and live chiefly in depths of over 1,000 -fathoms, the eyes are either very small or absent.</p> - -<p class='c007'>Some interesting examples may be found in the -species of widely distributed genera to illustrate -these points. Thus in <i>Neobythites grandis</i>, from -1,875 fathoms, the eye is small, only one-eleventh -the length of the head, but in <i>Neobythites macrops</i>, -<i>N. ocellatus</i>, and <i>N. gillii</i> from shallower water it is -much larger.</p> - -<table class='table1' summary=''> - <tr><td class='c014' colspan='4'><span class='pageno' id='Page_70'>70</span></td></tr> - <tr> - <td class='c010'>N. grandis</td> - <td class='c009'>1,785 fms. Eye</td> - <td class='c015'><span class='fraction'>1<br /><span class='vincula'>11</span></span>th</td> - <td class='c016'>length of the head</td> - </tr> - <tr> - <td class='c010'>N. macrops</td> - <td class='c009'>375 fms. Eye</td> - <td class='c015'><span class='fraction'>2<br /><span class='vincula'>9</span></span></td> - <td class='c016'>length of the head</td> - </tr> - <tr> - <td class='c010'>N. ocellatus</td> - <td class='c009'>350 fms. Eye</td> - <td class='c015'>¼</td> - <td class='c016'>length of the head</td> - </tr> - <tr> - <td class='c010'>N. gillii</td> - <td class='c009'>111 fms. Eye</td> - <td class='c015'><span class='fraction'>1<br /><span class='vincula'>3⅔</span></span></td> - <td class='c016'>length of the head</td> - </tr> -</table> - -<p class='c007'>Similarly in the species of the widely distributed -deep-sea genus <i>Macrurus</i>: the species <i>M. parallelus</i>, -<i>M.<a id='t70'></a> japonicus</i>, <i>M. fasciatus</i>, &c., usually living in water -less than 1,000 fathoms deep, have large and in some -cases very large (<i>M. fasciatus</i>) eyes, but <i>Macrurus -filicauda</i>, <i>M. fernandezianus</i>, <i>M. liocephalus</i>, <i>M. -Murrayi</i>, <i>M. armatus</i> have small eyes.</p> - -<p class='c007'>Some deep-sea fish have their eyes reduced to -a mere rudiment; such as <i>Ceratias uranoscopus</i>, <i>C. -carunculatus</i>, <i>Melanocetus Murrayi</i>, <i>Typhlonus nasus</i>, -and <i>Aphyonus gelatinosus</i>, but not even a rudiment -of an eye is to be found in <i>Ipnops Murrayi</i>.</p> - -<p class='c007'>But the fish of the greatest depths are by no means -always characterised by small eyes. <i>Malacosteus</i>, a -typical deep-sea form, has very large eyes, and so -have <i>Bathylagus</i>, living in the enormous depth of -3,000 fathoms, and <i>Bathytroctes</i>, in 1,090 and 2,150 -fathoms.</p> - -<p class='c007'>The result of recent deep-sea work, then, has been -to show that as we proceed from shallow shore water -to depths of 500 to 900 fathoms the eyes of the -fish become larger, but in greater depths than 1,000 -<span class='pageno' id='Page_71'>71</span>fathoms the eyes of some fish become considerably -reduced, but those of others become still more enlarged. -In the greatest depths of the ocean in fact -it seems very probable that nearly all the fish are -characterised by either very large eyes or very small -ones.</p> - -<p class='c007'>We cannot expect to learn very much at present -from the study of the eyes of deep-sea mollusca. -The Cephalopods form the only class of this Phylum -whose genera invariably possess large and well-developed -eyes, and there does not seem to be any -very marked increase or decrease in the size of the -eyes of the few deep-sea cuttlefish that are known -to us.</p> - -<p class='c007'>The eye of <i>Nautilus</i> is certainly remarkably -interesting, but as this genus is the only representative -of its order, and is known at times to float -upon the surface of the ocean, it would certainly be -erroneous to attribute the peculiarity of the structure -of its eye to its ‘temporary’ deep-sea habits. We are -still ignorant of the usual habitat of the remarkable -genus <i>Spirula</i>, notwithstanding the fact that many -of the tropical beaches are very largely composed of -its empty shells. Whether it is a deep-sea dweller or -not, we know nothing at present of the character of -<span class='pageno' id='Page_72'>72</span>its eye, so that it can throw no light upon the problems -we are now discussing.</p> - -<p class='c007'>Among the deep-sea gasteropods we find the -same irregularity in the possession of eyes that we -have just described among fishes. Thus a species of -<i>Pleurotoma</i>, dredged by the ‘Porcupine,’ in 2,090 -fathoms, has a pair of well-developed eyes on short -footstalks, but <i>Pleurotoma nivalis</i>, obtained by the -‘Talisman,’ is blind. Again a species of <i>Fusus</i>, obtained -by the ‘Porcupine,’ in 1,207 fathoms, is provided -with well-developed eyes, but <i>Fusus abyssorum</i>, -obtained by the ‘Talisman,’ is blind. Among the -Lamellibranchs there are very few genera that possess -well-marked eyes. The genus <i>Pecten</i> is one of those -that in shallow waters possess numerous highly complicated -visual organs situated on the edge of the -mantle. In the deep-sea species, <i>Pecten fragilis</i>, these -eyes are wanting, but we have not sufficient evidence -at present to enable us to assert that all the deep-sea -species of this genus are blind.</p> - -<p class='c007'>Among the Crustacea there is a very general -tendency to lose the eyes at a depth of a few hundred -fathoms of water.</p> - -<p class='c007'>In <i>Ethusa granulata</i>, for example, the eyes disappear -at 500 fathoms and the eye-stalks become -<span class='pageno' id='Page_73'>73</span>firmly fixed, greater in length, and take the place -of the rostrum which disappears. In some forms—such -as <i>Thaumastocheles zaleuca</i> and <i>Willemoesia</i>—the -eye-stalks themselves have completely disappeared.</p> - -<p class='c007'>In the deep-sea Isopoda some forms lose their eyes -entirely, but <i>Bathynomus giganteus</i> possesses a pair -of enormous eyes, each provided with 4,000 facets.</p> - -<p class='c007'>To illustrate the distribution of eyes in this group, -we may take as an example the genus <i>Serolis</i>. All -the species of this genus are provided with eyes -except <i>Serolis antarctica</i>—a species that extends from -600 to 1,600 fathoms.</p> - -<p class='c007'>The eyes of all the deep-sea species are relatively -larger than those of the shallow-water ones, except -<i>Serolis gracilis</i>, whose eyes seem to be disappearing.</p> - -<p class='c007'>But these large eyes of the deep-sea species of -<i>Serolis</i> are not capable of any greater perceptive -power. In fact, the evidence of degeneration they -show, both in minute structure and in the diminution -of pigment, proves that they can be of very little use -to these animals for perception (see Figs. 4 and 5).</p> - -<p class='c007'>This increase in size, accompanied by degeneration -of structure, is just what we should expect to find in -the eyes of deep-sea animals, and it is difficult to -<span class='pageno' id='Page_74'>74</span>explain why it is that we do not find more examples -of it.</p> - -<p class='c007'>If the animals that now live in the depths of the -sea are descended from the shallow-water forms of -bygone epochs, they must have passed through many -different habitats with diminished light until they -reached their present dark abode in the abyss.</p> - -<div class='figcenter id003'> -<img src='images/fig_004.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 4<a id='fig4'></a>.</span>—Semi-diagrammatic section through the eye of <i>Serolis schythei</i>, a shallow-water species (4–70 fathoms). <span class='fss'>C</span>, lens; <span class='fss'>V</span>, crystalline cone; <span class='fss'>R</span>, rhabdom; <span class='fss'>N</span>, nerve. (After Beddard.)</p> -</div> -</div> - -<div class='figcenter id003'> -<img src='images/fig_005.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 5<a id='fig5'></a>.</span>—Diagrammatic section of the eye of <i>Serolis bromleyana</i>, a deep-sea species (400–1,975 fathoms), showing the degenerate character of the eye. The corneal facets <span class='fss'>C</span>, and the crystalline cones <span class='fss'>V</span>, are the only structures that can be recognised. (After Beddard.)</p> -</div> -</div> - -<p class='c007'>In every new region they came to, the forms with -larger and better eyes would be at an advantage in -the fainter light, and would be more likely to survive -<span class='pageno' id='Page_75'>75</span>and transmit their favourable variation in this respect -to their offspring than their less fortunate neighbours. -Thus down to the depth of the limit of sunlight we -should expect to find, as we do find in fishes, large-eyed -species.</p> - -<p class='c007'>Beyond the limit of direct sunlight the eyes would -be of very little use to them, the pigment would disappear -and the tissues become degenerate. This is -precisely what has occurred in the genus <i>Serolis</i>.</p> - -<p class='c007'>The disappearance of the sense of sight in the -animals of the deep sea is sometimes accompanied by -an enormous development of tactile organs.</p> - -<p class='c007'>Thus, among fishes we find <i>Bathypterois</i>, a form -that possesses extremely small eyes, provided with -enormously long pectoral fin rays that most probably -possess the functions of organs of touch.</p> - -<p class='c007'>Among the Crustacea we find the blind form, -<i>Galathodes Antonii</i>, with an extraordinary development -in length of the antennæ, and <i>Nematocarcinus</i>, with -enormously long antennæ and legs.</p> - -<p class='c007'>The subject of the power of emitting phosphorescent -light possessed by some deep-sea animals is much -more difficult to deal with.</p> - -<p class='c007'>The presence of distinct organs in many of the -deep-sea fish that can only be reasonably interpreted -<span class='pageno' id='Page_76'>76</span>as phosphorescent organs, the presence of well-developed -and evidently functional eyes in many deep-sea -animals, and many other considerations render it -very highly probable that some, if not many, forms -emit a phosphorescent light.</p> - -<p class='c007'>The power and constancy of the light emitted, -however, must for the present remain a matter of -conjecture. We cannot judge at all of the amount -of light given out by an animal in deep water by its -appearance when thrown out of a dredge upon the -deck. Whether the phosphorescent light given out -by an Alcyonarian or a Crustacean is more or less at -a temperature of 40° Fahr. and a pressure of one ton -per square inch than it is at 60° Fahr. and the ordinary -barometric pressure of the sea-level, is a question -that has not yet been brought to an experimental test.</p> - -<p class='c007'>Whatever the answer to this question may be, -the fact remains that a greater percentage of animals -from the deep sea exhibit some sort of phosphorescent -light when brought on deck than animals that live -in shallow water.</p> - -<p class='c007'>The curious organs possessed by some fishes that -are supposed to be organs for the emission of phosphorescent -light have recently been subjected to a -minute examination by von Lendenfeld.</p> - -<p class='c007'><span class='pageno' id='Page_77'>77</span>It has been known for some years now, that the -slime secreted by the skin glands of certain sharks -is highly phosphorescent. It is not difficult, then, -to understand how it came about that certain fish -developed complicated phosphorescent organs.</p> - -<p class='c007'>From the phosphorescent slime secreted by a simple -skin gland to the most complicated eye-like phosphorescent -organ, we have a series of intermediate -forms that are quite sufficient, even in the imperfect -state of our knowledge at the present day, to enable -us to understand the outlines of the evolution of these -peculiar and interesting organs.</p> - -<p class='c007'>We can distinguish two kinds of phosphorescent -organs in the deep-sea fish. There are the curious -eye-like or ocellar organs situated usually in one or -more rows down the sides of the fish’s body, forming -as it were a series of miniature bull’s-eye lanterns to -illuminate the surrounding sea (fig. <a href='#fig6'>6</a>); and various -glandular organs that may be situated at the extremity -of the barbels or in broad patches behind the eyes or -in other prominent places on the head and shoulders.</p> - -<p class='c007'>Ocellar organs have been known for many years -to occur on the sides of the interesting pelagic fish, -<i>Scopelus</i>. Most of the species of this genus live in -the open sea at moderate depths, coming to the surface -<span class='pageno' id='Page_78'>78</span>only at night, but other -species are found in almost -every depth down to 2,000 -fathoms of water.</p> - -<div class='figcenter id001'> -<img src='images/fig_006.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 6<a id='fig6'></a>.</span>—<i>Opostomias micripnus</i>; 2,150 fathoms. (After Günther.)</p> -</div> -</div> - -<p class='c007'>In <i>Opostomias micripnus</i>, a -dark black fish living at a -depth of over 2,000 fathoms, -there are two rows of ocellar -organs running down the sides -of the body from the head to -the tail. In the living animal -they are said to shine with a -reddish lustre. In addition -to these, the conspicuous organs, -there are groups of fifty, -a hundred, or even more very -much smaller organs situated -on the sides and back of the -fish, each of which is lenticular -in shape and consists of a -number of short polygonal -tubes containing a granular -substance with rounded bases -resting on the subjacent tissue. -The whole organ is covered -<span class='pageno' id='Page_79'>79</span>by a simple continuation of the cuticle of the body-wall. The granular substance contained in the tubes -is most probably the seat of luminosity.</p> - -<div class='figcenter id001'> -<img src='images/fig_007.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 7<a id='fig7'></a>.</span>—Head of <i>Pachystomias microdon</i> (after Von Lendenfeld). <span class='fss'>A</span>, anterior sub-orbital phosphorescent organ; <span class='fss'>B</span>, posterior sub-orbital phosphorescent organ.</p> -</div> -</div> - -<p class='c007'>As a type of the glandular organs we may take -one of the sub-orbital organs found on the head of -<i>Pachystomias microdon</i>.</p> - -<p class='c007'>In this fish there are two very conspicuous white -organs immediately below the eye. The anterior -one, which lies below and in front of the eye, is oval, -with its upper margin slightly concave. In section -it is seen to be surrounded by a thin layer of black -pigment, and to consist of a reticular glandular -substance in which is embedded a hammer-shaped -lens-like body. Between these two structures there -<span class='pageno' id='Page_80'>80</span>is interposed a thick layer of light reflecting -spicules.</p> - -<p class='c007'>The exact part that is played by the different -components of these curious phosphorescent organs is -not yet known, but sufficient has been said to indicate -to the reader the degree of complexity that these -organs may reach in the fish of the great depths of -the ocean.</p> - -<div class='figcenter id001'> -<img src='images/fig_008.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 8<a id='fig8'></a>.</span>—Section of the anterior sub-orbital phosphorescent organ of <i>Pachystomias microdon</i> (after Von Lendenfeld). <span class='fss'>L</span>, lens; <span class='fss'>O</span>, phosphorescent gland; <span class='fss'>P</span>, pigment sheath.</p> -</div> -</div> - -<p class='c007'>But the power of emitting phosphorescent light -is by no means confined to the group of fishes. Some -of the Macrurous Decapoda among the Crustacea -are known to be phosphorescent. In the case of -<i>Heterocarpus Alphonsi</i>, for example, the naturalists -of the ‘Investigator’ found that ‘clouds of a pale -<span class='pageno' id='Page_81'>81</span>blue highly luminous substance, which not only -illuminated the observers’ hands and surrounding -objects in the vessel in which the creature was confined, -but also finally communicated a luminosity to -the water itself, were poured out apparently from -the bases of the antennæ.’</p> - -<p class='c007'>‘The <i>Willemoesia</i>, too, was luminous at two circumscribed -points somewhere near the orifices of -the genital glands.’</p> - -<p class='c007'>Again, all the Alcyonarians dredged by the ‘Challenger’ -in deep water were found to be brilliantly -phosphorescent when brought to the surface, the -light consisting, according to Moseley, of red, -yellow, and green rays only.</p> - -<p class='c007'>Among the Echinoderms we have not many -recorded instances of a phosphorescent light being -emitted, but it is quite possible that many, if not all -of them, may possess this power. The curious deep-sea -form <i>Brisinga</i>, that was first discovered by Ch. -Asbjörnsen, is known to be so brilliantly phosphorescent -that it has been called a veritable <i>gloria maris</i>, and -writing of the curious brittle-star <i>Ophiacantha spinulosa</i> -(dredged by the ‘Porcupine’ in 584 fathoms of water), -Professor Wyville Thomson remarks that the light -was of a ‘brilliant green, coruscating from the centre -<span class='pageno' id='Page_82'>82</span>of the disc, now along one arm, now along another, -and sometimes vividly illuminating the whole outline -of the star-fish.’</p> - -<p class='c007'>According to Filhol many of the abysmal Annelid -worms are in the habit of emitting a vivid phosphorescent -light, and capable thereby of illuminating the -medium in which they live.</p> - -<p class='c007'>We have now considered all those characters exhibited -by deep-sea animals that may be associated -with the absence of direct sunlight. To run through -them again briefly we may say: that the deep-sea -species, belonging to classes of animals that usually -possess eyes, show some modification in the size of their -eyes, in that they are either very large, very small, -or altogether wanting. That deep-sea animals are -nearly always uniformly coloured. Very frequently -they are black or grey or white, less frequently -bright red, purple, or blue. But whatever the -colour may be, spots, stripes, bands, and other -markings of the body are very rarely seen. That -deep-sea animals are brilliantly phosphorescent, the -light being emitted either by special organs locally -situated on the head, body, or appendages, or by the -general surface of the body.</p> - -<p class='c007'>But there are some other characters that cannot -be thus associated with the absence of sunlight.</p> - -<p class='c007'><span class='pageno' id='Page_83'>83</span>In the first place bathybial fish, mollusca, crustacea, -and other animals usually possess a remarkably -small amount of lime in their bones and shells.</p> - -<p class='c007'>In fishes we are told that the bones have a fibrous, -fissured, and cavernous texture, are light, with -scarcely any calcareous matter, so that the point of -a fine needle will readily penetrate them without -breaking. In some the primordial cartilage is -persistent in a degree rarely met with in surface -fishes, and the membrane bones remain more or -less membranous or are reduced in extent, like the -operculum, which is frequently too small to cover -the gills.</p> - -<p class='c007'>This cannot be due in all cases to a deficiency of -carbonate of lime in the sea water, for we find these -characters well marked in some of the fish, such as -<i>Melanocetus Murrayi</i>, <i>Chiasmodus niger</i>, and <i>Osmodus -Lowii</i>, that are found on the Globigerina mud.</p> - -<p class='c007'>Then again, the shells of the deep-sea Lamellibranchs, -Gasteropods, Brachiopods, and Crustacea -are very frequently remarkably thin and transparent, -a character that is probably more generally due to -a weakness in absorptive or secretive activity than -to a deficiency in the supply of lime.</p> - -<p class='c007'>There are one or two characters of the deep-sea -<span class='pageno' id='Page_84'>84</span>fish that it is not easy to account for, and it is -necessary only to mention their occurrence without -attempting to offer any explanation of them.</p> - -<p class='c007'>One of the most common of these is the very -dark pigment occurring in certain parts of the -epithelium of the mouth and respiratory passages -and the endothelium of the peritoneum. For example, -in <i>Bathysaurus mollis</i>, living at a depth of -2,000 fathoms, the mouth and buccal cavities are black. -The same thing occurs in <i>Ipnops Murrayi</i>, and indeed -in all the strictly deep-sea forms.</p> - -<p class='c007'>Another important character of very frequent -occurrence is the reduction in size, length, and number -of the gill laminæ.</p> - -<p class='c007'>Among invertebrates we may mention as a fact -of some interest, dependent perhaps on the soft -character of the bottom, the preponderance of stalked -forms over those of more sessile habits.</p> - -<p class='c007'>Thus among the Alcyonaria the characteristic -forms of the deep water are the Pennatulids, and -more particularly the genus <i>Umbellula</i> with its long -graceful stem and terminal tuft of polyps. Among -the Echinoderma we find many forms of stalked -Crinoids. Among the Tunicates several curious -genera characterised by their long peduncles.</p> - -<p class='c007'><span class='pageno' id='Page_85'>85</span>Taking the fauna as a whole, Moseley regarded it -as similar in some respects to the flora of the high -mountains. Some forms are dwarfed in size, such as -the species of Radiolaria, Cerianthus, some of the -Cephalopods, &c., while others are very much larger -than their shallow-water allies, such as the Pycnogonids, -nearly all the Crustacea, Alcyonarians (as -regards the size of the polypes), Siphonophora, and -many others.</p> - -<div class='chapter'> - <span class='pageno' id='Page_86'>86</span> - <h2 class='c005'>CHAPTER V<br /> <span class='large'>THE PROTOZOA, CŒLENTERA, AND ECHINODERMA OF THE DEEP SEA</span></h2> -</div> - -<p class='c006'>The most important, but perhaps somewhat disappointing, -result of the deep-sea researches of recent -years has been to prove that the abysmal fauna does -not possess many very extraordinary forms.</p> - -<p class='c007'>It seemed probable, before the dispatch of the -‘Challenger’ expedition, that when the dredge and -the trawl should be successfully employed in depths -of over 2,000 fathoms, a new and remarkable fauna -would be brought to light. Some naturalists thought -it even possible that, not only would many genera -be found alive that are known to us only by their -fossilised skeletons in the secondary and tertiary rocks, -but that there might be many other new creatures -whose anatomy would throw much light on the -theories of the evolution of the animal series.</p> - -<p class='c007'>But none of the great expeditions that have sailed -since the year 1874 have yet succeeded in showing -<span class='pageno' id='Page_87'>87</span>that the hopes and wishes of these naturalists were -really justified. Although thousands of species of -animals have been described in the volumes that -have been devoted to deep-sea work, the number of -the sub-kingdoms and classes remains the same, -and indeed the number of new families and genera -has not been increased in any very unprecedented -manner.</p> - -<p class='c007'>We have found no animals in the depths of the -sea of such interest and importance as Ornithorhynchus, -Amphioxus, Balanoglossus, Peripatus, -Millepora, or Volvox among the living, or Hipparion, -Archæopteryx, Ammonites, Slimonia, and the Trilobites -among extinct animals.</p> - -<p class='c007'>The abysmal fauna is not in fact remarkable for -possessing a large number of primitive or archaic -forms. It is mainly composed of a number of species -belonging to the families and genera of our shallow-water -fauna that have, from time to time, migrated -into greater depths and become modified in their -structure in accordance with the extraordinary conditions -of their new habitat.</p> - -<p class='c007'>There is very good reason to believe that this -migration has been going on from time immemorial, -and consequently we find a few forms typical of the -<span class='pageno' id='Page_88'>88</span>bygone times, left to struggle for existence with -the more recent immigrants from shallow waters. -But after all the proportion of ancient forms to -modern ones in the fauna of the abyss is not larger -than it is in the fauna of fresh-water lakes and -streams or even of the dry land. Nor is there any -reason why it should be. The land and the fresh -water have been peopled by migrations from the -shallow water of the sea from generation to generation -in precisely the same way, and they each can -show a certain number of archaic forms.</p> - -<p class='c007'>We must now consider briefly some of the most -interesting deep-sea representatives of the various -classes of the animal kingdom, referring as we pass -on to the extent to which these classes contribute -to the fauna of the abyss.</p> - -<p class='c007'>We find a great difficulty in determining with -any degree of certainty the actual depths at which -the supposed abysmal forms of Protozoa actually -live. All the Radiolaria and Foraminifera—the only -Protozoa that are largely represented in the fauna of -the open seas—are planktonic in habit; that is to say, -they float or drift about in the water without ever -becoming attached to the sea bottom; and when the -contents of a dredge, that has been hauled up from a -<span class='pageno' id='Page_89'>89</span>great depth, are examined, it is impossible to say at -what points in its long journey from the bottom the -Protozoa it contains were caught. Even if dredges -and nets are used which can be closed by a messenger -at any particular depth, the problem cannot be very -easily settled; for even if the protozoa shells that are -captured are found to contain a certain amount of -protoplasm, it must be proved that that protoplasm -is actually alive when brought on deck before we -know for certain that the species actually live on the -bottom. When the pelagic Foraminifera and Radiolaria -die and sink to the bottom, their protoplasm -probably disintegrates very slowly, and it is quite -probable that the floor of the ocean is littered with -the shells of truly pelagic protozoa, each containing a -greater or smaller amount of undecomposed protoplasm.</p> - -<p class='c007'>However, there is little doubt that there are -some truly abysmal Protozoa. Among the Radiolaria, -for example, it seems extremely probable -that the majority of the Phæodaria and many Spumellaria -live only in very deep water. ‘A character -common to these abyssal forms,’ says Haeckel, ‘and -not found in those from the surface or slight depths, is -found in their small size and massive heavy skeletons, -<span class='pageno' id='Page_90'>90</span>in which respects they strikingly resemble the fossil -Radiolaria of Barbadoes and Nicobar islands.’ The -Phæodaria are very widely distributed over the floor -of the ocean, and occur in some districts in such -numbers that the ‘Challenger’ was able to bring home -some hundreds of thousands of specimens. They are -distinguished from other Radiolaria by the thick outer -and thin inner capsule, by the typical main opening -or atropyle placed on the oral pole of the main axis -with a radiate operculum provided with a tubular -proboscis, and lastly by the presence -of the phæodium, a voluminous pigment -body which lies invariably on -the oral half of the calymma and -is composed of numerous singular -pigment granules of green, olive, -brown, or black colour.</p> - -<div class='figleft id004'> -<img src='images/fig_009.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 9<a id='fig9'></a>.</span>—<i>Challengeria Murrayi</i>, one of the Phæodaria (2,250 fathoms). <span class='fss'>A</span>, phæodium; <span class='fss'>B</span>, central capsule; <span class='fss'>C</span>, strands of protoplasm in the calymma. After Haeckel.</p> -</div> -</div> - -<p class='c007'>There are many genera belonging -to the Foraminifera that are -very probably inhabitants of abysmal -depths, but they do not seem -to possess any special characters, -unless it be a greater thickness and density of -their shells, to distinguish them from their shallow-water -allies.</p> - -<p class='c007'><span class='pageno' id='Page_91'>91</span>Passing now to the group of the sponges or -Porifera, we find that the calcareous sponges are not -represented at all in the abysmal zone. Two species -are found at a depth of 450 fathoms, but none are -truly bathybial in habit. The same remark applies -to the horny sponges. These forms chiefly belong -to the littoral or very shallow-water fauna, and never -descend to greater depths than 400 fathoms. Of the -other groups of Porifera—the Monaxonia, the Tetractinellidæ, -and the Hexactinellidæ—several genera are -known to extend down to some of the greatest depths -at which trawling operations have been successfully -carried on. It is difficult to point to any characters in -these sponges that can be attributed in any way to the -conditions of deep-sea life, but nevertheless we do find -in deep water some of the most remarkable and beautiful -forms of sponge skeleton that can be found anywhere.</p> - -<p class='c007'>Amongst the Cœlentera we find in the deep water -a remarkable sub-family of Medusæ, which has been -named by Haeckel the Pectyllidæ. It is distinguished -from the other jelly-fish by the curious sucking cups -situated at the ends of the tentacles. It seems probable -that they are used for purposes of locomotion, the -animal walking over the muddy bottom as on a -series of stilts.</p> - -<p class='c007'><span class='pageno' id='Page_92'>92</span>Like most of the deep-sea Hydroids, the Pectyllidæ -are usually devoid of sense organs, but a single -specimen of <i>Periphylla mirabilis</i>, captured by the -naturalists of the ‘Challenger,’ possessed well-marked -eyes.</p> - -<p class='c007'>There is also a peculiar family of the Siphonophora, -called the Auronectæ, consisting of a few specimens -that have been hitherto found only in very deep -water. Like the well-known Portuguese man-of-war -<i>Physalia</i> of the surface waters, the Auronectæ -possess a large swimming bladder or pneumatophore, -but they have in addition another peculiar bladder-like -cavity, called the aurophore, communicating with it, -which may be an organ for secreting gas.</p> - -<p class='c007'>A very interesting genus allied to Velella was also -found in depths of over 2,000 fathoms by the ‘Challenger’ -expedition. It is supposed to be a survival -of the ancestral form of the Disconectæ, or, at any -rate, to be a link connecting the Siphonophora with -the Medusæ. The very well marked octoradial -arrangement of the parts of <i>Discalia</i>, as this genus -has been termed, is certainly a point of great interest -and importance.</p> - -<p class='c007'>There is no large family of the sea anemones that -is peculiar to deep water, but several genera that -<span class='pageno' id='Page_93'>93</span>occur only in the abyss exhibit some curious modifications. -The manner in which the tentacular pores -have become enlarged, and the tentacles themselves -diminished in size and flexibility, has already been -referred to in a previous chapter (p. <a href='#Page_36'>36</a>).</p> - -<p class='c007'>The family of sea anemones that has been named -the Corallimorphidæ, characterised by the stiffness -and slight contractility of the body, the knobbed -nature of the tentacles, and their distribution in -several series, was, until quite recently, considered to -be a true abysmal family. The two species, <i>Corallimorphus -rigidus</i> and <i>C. profundus</i>, are known to occur -only in very deep waters, and present some curious -modifications of structure in relation to their habit; -but it seems probable that to this family should -be added the remarkable littoral form <i>Thelaceros -rhizophoræ</i> found on the coast of Celebes attached -to the roots of the mangrove trees in the swamps.</p> - -<p class='c007'>The fact that all the principal groups of the -Actiniaria, except, perhaps, the group that includes -those forms with only eight mesenteries, the Edwardsiæ, -have representative genera or species in the great -depths of the ocean, points to the conclusion that the -sea anemones have migrated from the shallow waters -in comparatively recent times, and that the migrations -<span class='pageno' id='Page_94'>94</span>have been successive, each period of their history -sending some specimens to survive or to become -extinct in the struggle for life in the deep sea.</p> - -<p class='c007'>Of the Madreporarian corals, several genera are -now known to inhabit very deep water, but they do -not present many very remarkable points of divergence -from the shallow-water forms.</p> - -<p class='c007'>It is true that as we pass from the shallow waters, -of those parts of the world where the great colonial -madrepores build up the greater part of the vast coral -reefs, into the deeper water beyond them, the solitary -forms become relatively more abundant, but no new -groups characterised by any special deep-sea attributes -make their appearance. We must remember, not only -that a great many solitary corals occur in shallow -water in different parts of the world, but that some -colonial forms, such as <i>Lophohelia prolifera</i> for example, -are found only in very deep water.</p> - -<p class='c007'>Until quite recently it was usually stated in works -dealing with the structures of coral reefs that the -so-called reef-building corals, that is to say the large -madrepores, astræids, and others, are confined to water -not deeper than thirty fathoms. This limit must -now be somewhat extended, in consequence of the -discovery by Captain Moore of an abundance of -<span class='pageno' id='Page_95'>95</span>growing coral at a depth of forty-four fathoms in the -China seas; but, nevertheless, it is perfectly true that -the corals do not grow in such profusion in very deep -water as to form anything that can be compared with -the reefs of the shores. It is quite possible that the -advantages afforded by the light, warmth, and abundance -of food of the shallow water may account for -the luxuriance and vigour of the reef corals, and that -where the food is scarce, and the water cold and dark -as it is below fifty fathoms, the power of continuous -gemmation is lost, and the rapidity of the growth and -reproduction of the individual polyps is considerably -diminished.</p> - -<p class='c007'>The fact remains, however, that, as with the sea -anemones, so with the madrepores, nearly all the -great divisions have a few isolated representatives in -the abyss, and that no great family occurring in large -numbers has yet been discovered peculiar to this zone.</p> - -<p class='c007'>The Alcyonaria, on the other hand, do present us -with at least one example of a true deep-sea family. -This great class of Anthozoa, distinguished from the -Zoantharia by the presence of not more than eight -tentacles and mesenteries and by the pinnate character -of the former, falls into four principal divisions. The -Stolonifera, the Alcyonidæ, the Gorgonidæ, and the -<span class='pageno' id='Page_96'>96</span>Pennatulidæ. The first three of these divisions -principally inhabit the shallow water. Each of them -sends a few representatives into the great depths, but -by far the greater number of the genera and species -are to be found between tide-marks or in depths of -less than fifty fathoms.</p> - -<p class='c007'>The Pennatulids, on the other hand, are rarely -found in very shallow water, and nearly half the -known genera live in deep water. At least two -families may be said to be characteristically abysmal. -These are the Umbellulidæ and the Protoptilidæ.</p> - -<p class='c007'>The Pennatulidæ are regarded by naturalists as -the most complicated or highly organised group of -the Alcyonaria. Three different forms of polype build -up the colony or sea-pen as it is called. There is -a single very much modified and enormously large -polype, without tentacles, forming the axis, a large -number of ordinary Alcyonarian polypes (autozooids) -arranged in the form of leaves, or simply scattered -irregularly on the surface of the central polype, and -a number of very small undeveloped polypes -(Siphonozoids) without tentacles, whose function -seems to be to pump water into the canals of the -colony, and thus to keep up the circulation of water.</p> - -<div class='figcenter id003'> -<span class='pageno' id='Page_97'>97</span> -<img src='images/fig_010.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 10<a id='fig10'></a>.</span>—Umbellula Güntheri. Nat. size. After Agassiz.</p> -</div> -</div> - -<p class='c007'><span class='pageno' id='Page_98'>98</span>The deep-sea genus <i>Umbellula</i> possesses a very -long and delicate axial polype, and the Autozooids and -Siphonozooids form a little cluster only at its extreme -summit. The small number of these polypes and -the very limited area over which they extend are the -two most characteristic features of the genus. It -would take me too far into the anatomy of the group -if I were to add any further details; but I cannot pass -on without noting that the whole structure of -Umbellula shows that it is far more primitive and -simple than the shallow-water genera. And, generally -speaking, this holds good for all the deep-sea Pennatulids. -In fact, we have here one of the rare examples -of a series of genera, that can be regarded as -a slightly modified ancestry of the shallow-water -genera, that has been brought to light by the exploration -of the abysmal depths of the ocean.</p> - -<p class='c007'>We have seen, then, that of the Cœlentera, the -only order that has a large proportion of its genera -living in deep water, is the only one whose members -all possess a stalk by which they fix themselves into -the mud or sand at the bottom of the sea.</p> - -<p class='c007'>It is not uninteresting to note, then, in passing -on to the Echinoderma, that the stalked Crinoids, the -only Echinoderms that can permanently fix themselves -to the bottom, are nearly all found in deep water.</p> - -<p class='c007'><span class='pageno' id='Page_99'>99</span>Several years before the ‘Lightning’ was -despatched on her memorable pioneering voyage, -Vaughan Thomson had proved that the common -feather star of the shallow waters of the British -coasts passes through a stage in its development which -resembles the fossil genera of the order in being -provided with a stalk for attachment.</p> - -<p class='c007'>But it was left for the naturalists of the -‘Porcupine,’ the ‘Challenger,’ the ‘Talisman,’ and -other vessels employed in deep-sea researches to prove -that adult stalked Crinoids are still living in nearly -all parts of the world at the great depths of the sea.</p> - -<p class='c007'>The genera of stalked Crinoids now living -are the remains of a family that at one time had -many representatives in all parts of the world. -Nearly all the marine deposits of bygone epochs, -including even those of such remote periods as the -Cambrian and Sub-Silurian, contain the fossilised -skeletons of these Crinoids. In some strata they are -represented by only a few genera, but in others they -are found in such enormous numbers that the seabeds -of those early times must have been literally -carpeted with them.</p> - -<p class='c007'>At the present day the few genera that survive -have been driven from the shore waters, and are -<span class='pageno' id='Page_100'>100</span>chiefly found at depths of more -than 200 fathoms, a few only -extending into 140 and even -70 fathoms.</p> - -<div class='figleft id005'> -<img src='images/fig_011.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 11<a id='fig11'></a>.</span>—<i>Rhizocrinus lofotensis</i>, one of the deep-sea stalked Crinoids. (After Carpenter.)</p> -</div> -</div> - -<p class='c007'>There are six genera known, -and of these, two, <i>Hyocrinus</i> -and <i>Bathycrinus</i>, are not found -in less than 1,000 fathoms of -water.</p> - -<p class='c007'>There can be no doubt that -these modern stalked Crinoids -are closely related to many of -those that flourished in bygone -periods of the history of the -earth. As Carpenter has -pointed out, the family Pentacrinidæ -are remarkable for -their long geological history. -The genus <i>Pentacrinus</i> itself -first appeared in the Trias and -persisted through the Secondary -and Tertiary times to the present -day.</p> - -<p class='c007'>The general character of -the fossil Pentacrinidæ is essentially -<span class='pageno' id='Page_101'>101</span>the same as that of their recent representatives, -except that they often had much longer -stems which reached to a length of as much as 50 or -even 70 feet; while the number of arms was frequently -limited to ten, which is not the case in any recent -species but <i>Pentacrinus naresianus</i>.</p> - -<p class='c007'>But the deep-sea Echinoids, or sea-urchins, -also present some features of particular interest. -Professor Agassiz in his report says, ‘One of the -very first results clearly indicated by the deep-sea -dredgings of Count Pourtales and the subsequent -investigations of the “Porcupine” expedition was the -antique character of the new genera discovered in -deep water, and especially their resemblance to -the cretaceous genera; and the study of the “Challenger” -Echinoids has brought this out still more -clearly.’</p> - -<p class='c007'>No fewer than twenty-four genera extend into the -abysmal regions; of these no less than sixteen, nearly -all belonging to a new group of Spatangoids, do not -live at all in shallow water.</p> - -<p class='c007'>The most interesting forms among these are the -Pourtalesiæ, a group that has existed since the Chalk. -These are heart-shaped urchins with a very peculiar -test. ‘They all have large coronal plates, recalling -<span class='pageno' id='Page_102'>102</span>the Echini, with a disconnected apical system -characteristic of many cainozoic spatangoids; they -have a sunken anal system, some of them a most -remarkable anal beak and a very striking pouch in -which the mouth is placed.’ They are found only in -very deep water, and have no allies among the modern -littoral fauna.</p> - -<p class='c007'>The genera <i>Calveria</i> and <i>Phormosoma</i> are two of -the most abundant Echinoids found in deep water, and -they are both representatives of forms that were very -abundant in cretaceous times. They are remarkable -for the extreme flexibility of their shells. In shallow-water -sea-urchins the shells are composed of a great -number of little plates that fit so closely to one -another that no movement is possible between them. -When the animal dies all the soft tissues decay -and the shell remains, to be tossed about by the -waves until crunched or dashed to pieces. In -<i>Phormosoma</i>, however, the tiny plates of which the -shell is composed are freely movable on one another, -and when the animal is alive very considerable contractions -and expansions can take place.</p> - -<p class='c007'>None of the modern shallow-water Echinoids -present this peculiarity, and it is a very interesting -and surprising fact that in this respect the fossils -<span class='pageno' id='Page_103'>103</span>of the chalk should resemble so closely the living -urchins of the abyss.</p> - -<p class='c007'>But before leaving the Echinoids reference must -be made to two more points that have been made by -the illustrious American naturalist. Agassiz points -out that all those genera that have the greatest -bathymetrical range, extending from the littoral to -the abysmal region, are at the same time genera which -date back to the Cretaceous period, while those -having a somewhat more limited range go back to the -tertiaries, and those that extend only slightly beyond -the littoral area go back only to the later tertiaries.</p> - -<p class='c007'>This interesting generalisation brings home to -our minds the enormous length of time that it must -have taken these animals to migrate from the shallow -to the deep sea. In the struggles for existence -between marine animals it must always have been -the last resort of those unable to compete with the -younger generations in shallow water to migrate -into the deeps.</p> - -<p class='c007'>The scarcity of food, the darkness, and the pressure -of these regions can never be so favourable for the -support of animals as the conditions of the shores. -We can well imagine that a species would take every -opportunity that is afforded to return from such -<span class='pageno' id='Page_104'>104</span>inhospitable habitats, and that only when, as it were, -every door is closed, when no island, continent, or -cape can afford it a free scope for life in shallow -water, does it become a true deep-sea species.</p> - -<p class='c007'>Steps taken towards the darkness in one period -may be retrieved in the next. The competing species -may itself have become extinct or have moved to -another locality. Organs may have become modified -or a new source of food supply tapped which enable -them to return once more to shallower waters. No -wonder that the steps in the progress, or rather retreat, -to the abyss have been the work of a time that can be -counted only by geological periods; and no wonder -then at the remark made by many deep-sea naturalists -that the abysmal fauna becomes poorer the -farther it is from shallow water.</p> - -<p class='c007'>The group of the Asteroidea, or star-fishes, contributes -largely to the fauna of the abyss.</p> - -<p class='c007'>During the voyage of the ‘Challenger’ no fewer -than 109 different species were found in depths of -over 500 fathoms, and in some localities a very large -number of star-fish were taken in one haul of the -dredge.</p> - -<p class='c007'>Nevertheless, there are not many abysmal genera -that differ to any remarkable degree from the littoral -<span class='pageno' id='Page_105'>105</span>ones; and indeed it may be said that the recent work -on deep-sea Asteroids does not throw much new light -either on the phylogeny of the group or on their -palæontological history.</p> - -<p class='c007'>The genus <i>Brisinga</i>, at one time supposed to be -a connecting link between the star-fishes and the -brittle stars (Ophiurids), has recently been shown to -be closely related to the families Heliasteridea, Echinasteridea, -and others typical of the class Asteroidea; -and, as Sladen has pointed out, the peculiarities of -structure that it exhibits are probably due to its extreme -isolation and the influence of its abysmal habitats.</p> - -<p class='c007'>But no work on the deep-sea fauna would be -complete without some reference to Brisinga. Discovered -by Asbjörnsen in 1853, in 200 fathoms of -water in the Hardanger fjord, and described in a -splendid memoir by the elder Sars, it excited great -interest among naturalists. The great brilliancy of -the phosphorescent light that it gave out on being -brought on deck, the remarkable tendency that it had -to cast off some of its numerous long, thin, ophiurid-like -arms, and some of the general features of its -internal anatomy were points that were considered at -the time to be sufficient to justify the establishment -of a separate sub-order for the family Brisingidæ.</p> - -<p class='c007'><span class='pageno' id='Page_106'>106</span>The more recent discovery, however, of genera -allied to Brisinga has bridged over the gap -separating it from other star-fish, and it is now -considered simply as the type of a family of the -order.</p> - -<p class='c007'>The numerous species of the genus that have been -found since Asbjörnsen’s original discovery are all -inhabitants of deep water, some of them going down -to the enormous depth of 2,000 fathoms; indeed there -are very few genera in the animal kingdom, containing -so many species as the genus Brisinga, that have such -a uniform deep-sea habitat.</p> - -<p class='c007'>The last group of Echinoderms that we have to -consider is the Holothurians. It contains one order—the -Elasipoda—that may be considered to be truly -bathybial, as there is only one species belonging to -it, <i>Elpidia glacialis</i>, that extends into water as shallow -as fifty fathoms.</p> - -<p class='c007'>The Elasipoda are remarkable for their strongly-developed -bilateral symmetry. Adult Echinoderms -as a rule possess a well-marked radial symmetry, as -we see exemplified in the feather-star, star-fish, and -sea-urchin, but this radial symmetry is only adopted -when they undergo their metamorphosis from the free -swimming and bilaterally symmetrical larval stage. -<span class='pageno' id='Page_107'>107</span>They are not born radially symmetrical, but become -so as they grow up. Moreover, we must bear in -mind that the radial symmetry of the adult only -obscures, it does not obliterate, the bilateral symmetry -of the larva.</p> - -<p class='c007'>In the Holothurian, however, we can always discover -a clear bilateral symmetry even in the adult. -That is to say, we can recognise an anterior and a -posterior end, a right and a left side of the body. It -is an organisation which emphasises, as it were, the -anterior and posterior ends, the right and left sides -and the dorsal and ventral surfaces that characterise -this interesting deep-sea order, the Elasipoda.</p> - -<p class='c007'>Here, then, we have an example of a character -common to all the larvæ of the sub-kingdom and exceptionally -well marked in the adults of a family -confined to deep-sea habitats.</p> - -<p class='c007'>Now we know that there is a tendency for some -of the peculiar characters of the ancestors of animals -to be recapitulated in the course of their development -from the egg, and accordingly most naturalists -are agreed that all the Echinoderms have descended -from some form of bilaterally symmetrical ancestor. -Are we, then, to believe that the Elasipoda brought -from the depths of the sea are more closely related -<span class='pageno' id='Page_108'>108</span>to these ancestral forms than the shallow-water -families?</p> - -<p class='c007'>The state of our knowledge at the present day -hardly allows us to answer this question very definitely. -However nearly they are related to such -ancestral Echinoderms in general form, they are -probably profoundly modified by a deep-sea life. -Nevertheless, in the simple shape of the calcareous -corpuscles of the skin, the simple form of the calcareous -ring, the communication of the water-vascular -system with the exterior by one or several pores, and -in some other anatomical characters, they give evidence -of their primitive characters.</p> - -<div class='chapter'> - <span class='pageno' id='Page_109'>109</span> - <h2 class='c005'>CHAPTER VI<br /> <span class='large'>THE VERMES AND MOLLUSCA OF THE DEEP SEA</span></h2> -</div> - -<p class='c006'>It has not been my intention in this volume to confine -my attention to the truly abysmal forms, but -rather to consider all those animals living in deep -water that show any characters strikingly different -from their relatives living in shallow water.</p> - -<p class='c007'>The term deep water is, after all, only a relative -one.</p> - -<p class='c007'>To one accustomed only to shore collecting, ten -fathoms is deep water, while on the other hand, to -such naturalists as those on board the ‘Challenger,’ -who are accustomed to dredge in all seas, nothing -under 1,000 fathoms is considered deep water.</p> - -<p class='c007'>We must bear in mind, however, that at a depth -of only 200 fathoms, the conditions of life are very -different to those of the shore waters. We find a -very great diminution in the amount of light, for instance, -that can penetrate through sea water teeming -<span class='pageno' id='Page_110'>110</span>with floating organisms of all kinds to reach the fauna -attached to the bottom at such a depth. The diminution -in the amount of light must mean a diminution -in the rapidity of growth of chlorophyll-bearing plants, -and consequently a diminution in the food supplies of -animals drawn from that source.</p> - -<p class='c007'>We might expect then to find, even in such shallow -water as this, some forms of particular interest. -It is true that the greater part of the fauna is made -up of ordinary shallow-water forms that have migrated -quite recently, and perhaps only temporarily, into the -depths, but we expect to find, and actually do find, the -outposts of a new fauna.</p> - -<p class='c007'>These remarks lead me to the consideration of -one or two very remarkable animals that have recently -been brought to light.</p> - -<p class='c007'>In that strange assembly of animals which, for -want of a better word, the authorities call the Vermes, -there are three groups whose relations to one another -and to the other groups of Vermes have been and still -remain a puzzle to naturalists.</p> - -<p class='c007'>These three groups are the Gephyrea, the Polyzoa, -and the Brachiopoda. In external form they are as -different from one another as possible.</p> - -<p class='c007'>The Gephyrea are solitary worm-like forms burrowing -<span class='pageno' id='Page_111'>111</span>in the sand or perforating rocks; the Polyzoa -are minute creatures that frequently build up by budding -large colonies which assume in some cases dendritic -forms like corals, and the Brachiopoda are protected -by thick bivalve shells simulating in a striking -manner the shells of the Lamellibranchiate mollusca.</p> - -<p class='c007'>But external form is not the only character that -can be relied upon for purposes of classification. The -general and minute anatomy, together with the story -of the development of these animals, teach us that -they are in some way closely related.</p> - -<p class='c007'>It is not within the scope of this book to enter -into the discussion of what these relations are; suffice -it to say that the controversy has within recent years -to a great extent turned upon the position in our -classification of three interesting genera. These are -Phoronis, Rhabdopleura and Cephalodiscus.</p> - -<p class='c007'>Phoronis occurs only in shallow water, Rhabdopleura -has been found in water from 40 to 200 -fathoms deep off the Shetlands and on the Norwegian -coasts, while Cephalodiscus was discovered by the -‘Challenger’ at a depth of 245 fathoms off Magellan -Straits.</p> - -<p class='c007'>Rhabdopleura forms colonies consisting of -branched tubes growing upon the tests of Ascidians, -<span class='pageno' id='Page_112'>112</span>on sea-weeds, corals, or other objects fixed to the sea bottom. -In the open, free extremity of each of the -branches may be found the polypide attached to a -filament or stalk which connects it with the other -polypides of the colony (fig. <a href='#fig12'>12</a>).</p> - -<div class='figcenter id003'> -<img src='images/fig_012.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 12<a id='fig12'></a>.</span>—A portion of a colony of <i>Rhabdopleura normani</i>. (After Lankester.)</p> -</div> -</div> - -<p class='c007'><span class='pageno' id='Page_113'>113</span>Each polypide is provided with a single pair of -large pinnate arms, resembling the arms of a -Brachiopod, and a broad muscular epistome by means -of which it is able to creep up or down the tube.</p> - -<p class='c007'>The affinities of this interesting creature are by -no means sufficiently well understood. It is one of -those forms that, without being, strictly speaking, -a connecting link between large and well-known -groups of animals, indicates to us some of the lines -of evolution that these groups may have passed -through; and, in so far as it does this, it has its -value and importance.</p> - -<p class='c007'>Cephalodiscus, though related to Rhabdopleura in -the presence of a structure corresponding to the -arms, and a broad epistome, seems to be more closely -connected with such a form as Balanoglossus in the -presence of a single pair of gill-slits, a small -rudimentary notochord and the position of the central -nervous system.<a id='r2' /><a href='#f2' class='c013'><sup>[2]</sup></a></p> - -<div class='footnote' id='f2'> -<p class='c007'><a href='#r2'>2</a>. A rudimentary notochord projecting forward from the buccal -cavity into the epistome has quite recently been discovered in -Rhabdopleura.</p> -</div> - -<div class='figcenter id003'> -<span class='pageno' id='Page_114'>114</span> -<img src='images/fig_013.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 13<a id='fig13'></a>.</span>—A single polypide of <i>Rhabdopleura normani</i>. <span class='fss'>M</span>, mouth; <span class='fss'>B</span>, epistome; <span class='fss'>S</span>, polypide stalk. (After Lankester.)</p> -</div> -</div> - -<p class='c007'><span class='pageno' id='Page_115'>115</span>Whatever position these genera may ultimately -occupy in our systems of classification, there can be -little doubt that much valuable information will be -obtained by a further study of their structure and -development—information that will probably shed -much light on the relationships to one another of the -many groups of Vermes. Their occurrence in water -of moderate depths only indicates perhaps that they -are gradually being crowded out from the more -favourable localities of shallow water, and are tending -towards extinction on the one hand, or a deep-sea -habitat on the other.</p> - -<p class='c007'>The Brachiopoda need not detain us long. Some -species are capable of existing at a great variety of -depths without any observable modification of shape -or characters. Thus <i>Terebratulina caput serpentis</i> -has the extraordinary bathymetrical distribution of -0–1,180 fathoms, and <i>Terebratula vitrea</i> 5–1,456 -fathoms. <i>Atretia</i> is the only genus peculiar to deep -water. It is a noteworthy fact in connection with -this order that the two genera, <i>Lingula</i> and <i>Glottidia</i>, -which compose the sub-order Ecardines, are both -confined to shallow water. Now the Ecardines are -anatomically, at any rate, the most primitive of the -Brachiopoda, and Lingula has the most ancient -geological history of any living genus of the animal -kingdom, shells almost identical with those of the -living species being found abundantly in the Cambrian -strata. Why it is that Lingula has been able to -<span class='pageno' id='Page_116'>116</span>maintain itself almost unchanged through all the -countless generations that have elapsed since -Cambrian times, and can now flourish amid the -desperate struggle for existence in the shallow waters -of the tropics, while its companions, the corals, -mollusks, arthropods, &c., have changed or passed -away, is one of those problems in natural history -that seem to us impossible of solution. The time -may come when we shall be able to appreciate better -than we do now the complicated relations between -animals and their environment, and then perhaps the -peculiar fitness of Lingula will be made manifest; -but at present we can but mention the fact as a fact, -and leave the solution of the problem to the future.</p> - -<p class='c007'>The order Gephyrea is probably another very -ancient group of animals, although in the absence -of any hard calcareous, siliceous, or horny skeleton -the geological record can give us no confirmation of -their antiquity. As with the Brachiopods so with -the Gephyrea, some of the species have a very wide -bathymetrical distribution. <i>Sipunculus nudus</i>, for -example, the commonest and best known of all the -Gephyrea, extends from quite shallow water to a depth -of over 1,500 fathoms. As Selenka has pointed out, -it is those Gephyreans that live in holes in stones, or -<span class='pageno' id='Page_117'>117</span>in shells such as <i>Phascolion</i> and <i>Phascolosoma</i>, that -are more frequently found at the greater depths; but, -apart from this, there are no characters that exclusively -belong to the abysmal Gephyrea or are more -frequently found in them than in the shallow-water -forms. Nor are there any genera, at present brought -to light, that are confined to those regions of the sea.</p> - -<p class='c007'>The group of the Annelida is not very well -represented in the deep-sea fauna. The genera -<i>Serpula</i> and <i>Terebella</i> have been found very widely -distributed over the earth, at all depths from the shore -to the abyss, but there do not seem to be many genera -that are confined to deep water. In some cases, where -there is a scarcity of lime in the water, the thin protecting -tubes of the sedentary forms are strengthened -by the adhesion of foreign particles, such as sponge -spicules and arenaceous foraminifera, but in others, -the tubes are formed of successive layers of a transparent -quill-like substance (<i>Nothria Willemoesii</i>) -which is frequently armed with spiny projections.</p> - -<p class='c007'>Most of the errant Polychætes found at great -depths are said to be most brilliantly coloured, and -some of these, such as <i>Eunice amphiheliæ</i>, have the -power of emitting a bright phosphorescent light; but -there seem to be no very definite and constant -<span class='pageno' id='Page_118'>118</span>characters separating these forms from the Polychætes -of shallow waters.</p> - -<p class='c007'>As is the case with many other orders of animals, -the species of Annelida living in deep water are -either blind or possess eyes of a remarkably large -size. <i>Genityllis oculata</i> may be taken as an example -of a deep-sea annelid with large eyes. This annelid, -belonging to the family Phyllodocidæ, was found at -a depth of 500 fathoms in the Celebes sea. It -possesses two enormous eyes which cover almost the -whole of the head, and there can be no doubt, from -the investigations of Dr. Gunn on their minute -anatomy, that they are perfectly functional.</p> - -<p class='c007'>Before leaving the Annelida a brief notice must -be made of the very extraordinary form <i>Syllis ramosa</i>, -found parasitic on a hexactinellid sponge at depths of -about 100 fathoms. It is chiefly remarkable for the -very complicated manner it has of producing buds -which do not immediately become detached from the -parent, but form a compound network which ramifies -through the interstices of the sponge like the colony -of a Hydromedusan.</p> - -<p class='c007'>Passing now to the sub-kingdom Mollusca, we -shall find that all the classes are represented in the -abysmal fauna.</p> - -<p class='c007'><span class='pageno' id='Page_119'>119</span>The Lamellibranchiata, or bivalves, occur in almost -all depths of the ocean, <i>Callocardia pacifica</i> and -<i>Callocardia atlantica</i> having been found at the enormous -depth of 2,900 fathoms. Some species, such as -<i>Venus mesodesma</i>, have a very wide bathymetrical -distribution, but others are only known to occur in -deep water.</p> - -<p class='c007'>Concerning the characters of the deep-sea -Lamellibranchiates, Mr. Smith, in his report on the -Lamellibranchia of the ‘Challenger’ expedition, says -‘very deep-water benthal species certainly have -a tendency to be without colour, and of thin structure, -no doubt resulting from the absence of light -the difficulty of secreting lime, the scarcity of food -and other unfavourable conditions of existence.’ But -notwithstanding this, the same author continues: ‘The -species are apparently few in number in comparison -with those of shallow water; and new and peculiar -generic forms which we naturally expected would -have been discovered are of even still rarer occurrence.’</p> - -<p class='c007'>As in the group of the Lamellibranchia, so in -the Gasteropoda, no very remarkable new genera or -species have been found in deep sea. Some shallow-water -genera, such as <i>Fusus</i> for example, have representative -<span class='pageno' id='Page_120'>120</span>species in the abyss; but, with the exception -of a want of brilliant coloration and marking and a -thinness of the shell, the deep-sea forms do not exhibit -any characteristic features. One of the most brightly -coloured shells found at great depths is that of <i>Scalaria -mirifica</i>, which is tinted rose and white, but this -seems to be quite an exceptional character among -the deep-sea Gasteropods. Several new genera were -found in the deep water, but their general characters -do not call for any special remark.</p> - -<p class='c007'>Among the Cephalopoda there seems to be little -doubt that the genera <i>Cirroteuthis</i>, <i>Bathyteuthis</i>, -and <i>Mastigoteuthis</i> are entirely abysmal, and the same -applies probably to one or two species of octopus; but -as Hoyle remarks, ‘apart from the single fact that -<i>Bathyteuthis</i> and <i>Mastigoteuthis</i> both have slender -filiform tentacles with minute suckers, no structural -features have been discovered which will serve to -diagnose a deep-sea form from a shallow-water one.’</p> - -<p class='c007'>The exact habitat of the interesting genus <i>Spirula</i> -is unfortunately still unknown. In some parts of -the tropics the shores are covered with spirula shells, -and yet the animals that secrete them are still to -be reckoned amongst the greatest rarities of our -museums. The numerous dredgings of the ‘Challenger’ -<span class='pageno' id='Page_121'>121</span>only brought to light one specimen of this -animal, and that from a depth of 360 fathoms, and the -‘Blake’ caught one at a depth of 950 fathoms, so that -there can be little doubt that <i>Spirula</i> lives in deep -water.</p> - -<div class='figcenter id003'> -<img src='images/fig_014.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 14<a id='fig14'></a>.</span>—<i>Bathyteuthis abyssicola.</i> (After Hoyle.)</p> -</div> -</div> - -<p class='c007'><span class='pageno' id='Page_122'>122</span>It seems to be very probable that some day, when -the right place and depth are discovered, <i>Spirula</i> -may be discovered in great abundance, but we have -at present no means of judging whether this will be -in very deep water or not.</p> - -<p class='c007'>Almost precisely similar remarks apply to the -distribution of the pearly Nautilus. The shells of -this Cephalopod are sometimes found in great number -on the shores of some of the islands of the Southern -Pacific Ocean and the Malay Archipelago, but the -living animal is but rarely captured. It has been -asserted by some travellers that the pearly Nautilus -floats on the surface of the ocean and possesses the -power of suddenly diving to great depths on being -disturbed; but it must be remembered that Rumphius -originally caught his Amboyna specimens of Nautilus -in traps set at a depth of 200 fathoms baited with -sea-urchins, and that the ‘Challenger’ captured a -single living specimen off Matuku island in 300 -fathoms.</p> - -<p class='c007'>The probability, then, is that both <i>Nautilus</i> and -<i>Spirula</i> should be included in the deep-sea fauna, but -we are still in want of a great deal more information -concerning their life and habits before this point can -be definitely determined.</p> - -<div class='chapter'> - <span class='pageno' id='Page_123'>123</span> - <h2 class='c005'>CHAPTER VII<br /> <span class='large'>THE ARTHROPODA OF THE DEEP SEA</span></h2> -</div> - -<p class='c006'>The deep-sea fauna seems to be particularly rich -in marine Arthropoda, many curious and interesting -forms being brought up with almost every haul of -the dredge. The Arthropoda, too, being very highly -organised animals, afford interesting and instructive -examples of the effect of abysmal life in the -modification of the sense organs and the production -of varieties specially modified for the conditions of -the struggle for existence in their strange habitat.</p> - -<p class='c007'>Concerning the groups of Ostracoda and Copepoda -it may be said that the evidence is not yet conclusive -that they include any truly deep-sea species. The -largest known Ostracod, measuring somewhat more -than an inch in length and probably allied to the -genus <i>Crossophorus</i>, has quite recently been captured -by Professor Agassiz at depths of less than 200 -fathoms, but he could obtain no evidence that it -descended into much deeper water than this.</p> - -<p class='c007'><span class='pageno' id='Page_124'>124</span>Mr. Brady, in writing the report of the ‘Challenger’ -Ostracoda, came to the conclusion that they do exist -in very limited numbers in the most profound depths -of the sea; but it is nevertheless quite possible that -all the Ostracods brought on deck by the trawl or -dredge were really captured either on the way down -or on the way up, and are, strictly speaking, pelagic -in habit.</p> - -<p class='c007'>Similar caution must be taken in dealing with the -Copepoda, an order of Crustacea that is essentially -pelagic in habit. The only species that has been -regarded as undoubtedly abysmal is <i>Pontostratiotes -abyssicola</i>, a form whose carapace and antennæ are -armed with exceedingly long and strongly toothed -spines, and was found in the mud brought up by the -trawl from a depth of 2,200 fathoms.</p> - -<p class='c007'><i>Calamus princeps</i>, the largest species of its genus -of a deep reddish brown colour, may also belong to -the fauna of the deep sea, but we have less evidence -concerning the habitat of <i>Hemicalamus aculeatus</i>, -<i>Phyllopus bidentatus</i>, and some of the Euchætæ.</p> - -<p class='c007'>The Amphipoda seem to be but poorly represented -in the fauna of the abyss; in fact it may be -considered to be still an open question whether any -Amphipods habitually live in very deep water.</p> - -<p class='c007'><span class='pageno' id='Page_125'>125</span>In the reports on the ‘Challenger’ Amphipoda, the -Rev. T. R. Stebbing states that thirty-one specimens -are known to come from great depths, but it would be -more correct to say that these specimens were found -in the dredges and trawls that had been lowered into -the great depths. It should be noticed, however, -that some of these specimens do show characters -that suggest, at any rate, that they come from deep -water. Thus the genus <i>Lanceola</i>, for example, is -characterised by the smallness of the eyes and a soft -membranous integument, while <i>Cystisoma spinosum</i>, -found in a dredge that had been at work at a depth -of over a thousand fathoms, has very large eyes.</p> - -<p class='c007'>In his report on the Crustacea of the ‘Norske -Nord-havns’ expedition, Professor Sars gives a full -description of many species of Amphipoda brought -by the dredge from depths of over 1,000 fathoms, -and nearly all of these were found to be quite -blind.</p> - -<p class='c007'>The form that seems to be most peculiar to the -great depths of the Northern Ocean is <i>Harpinia -abyssi</i>. It was found at no less than fifteen different -stations at depths ranging from 350 to 2,215 fathoms, -and is characterised by its large size and the total -absence of eyes.</p> - -<p class='c007'><span class='pageno' id='Page_126'>126</span>Another point that should be considered in -coming to any conclusion on the supposed habitat of -such forms, is the similarity or dissimilarity of widely -distributed species.</p> - -<p class='c007'>I have had occasion to point out in a previous -chapter the general similarity of the abysmal fauna -all over the world, a very striking phenomenon, commented -on by almost every naturalist who has had -a wide experience of this kind of investigation.</p> - -<p class='c007'>Among the Amphipoda we have a very striking -example of this. The species <i>Orchomene musculosus</i> -was taken by the ‘Challenger’ off the southern part of -Japan at a depth of 2,425 fathoms, the bottom being -red clay and the temperature 35·5° Fahr. The -species <i>Orchomene abyssorum</i> was taken off the east -coast of Buenos Ayres at a depth of 1,900 fathoms, -the bottom being blue mud and the temperature -33·1° Fahr. To the description of this last-named -species Mr. Stebbing adds, ‘had this species been -taken within reasonable distance of <i>O. musculosus</i>, -the resemblance is so great that one might have been -tempted to disregard the points of difference as due -to some other cause than difference of species.’</p> - -<p class='c007'>Such a striking similarity between two species -living so far apart from one another may, when we -<span class='pageno' id='Page_127'>127</span>take into consideration the depth, the character of the -bottom, and the temperature from which they are -supposed to have been dredged, be taken to support -very strongly the view that these species are really -abysmal in habit.</p> - -<p class='c007'>Among the Isopoda we have several very characteristic -forms—no fewer than nine distinct genera -peculiar to the abysmal zone have been described by -Beddard—and of these two, <i>Bathynomus</i> and <i>Anuropus</i>, -are to be regarded as types of sub-families. -They seem to be very unevenly distributed over the -floor of the ocean, some regions, such as the whole -of the Central and Southern Atlantic and the Central -and Western Pacific, produce none; whilst -the waters of the east coast of New Zealand, the -Crozets, and others, produce a great many varieties. -Many of the deep-sea Isopoda exhibit characters that -are usually associated with the bathybial life. Thus, -according to Beddard, thirty-four of the deep-sea -species are totally blind, and eighteen have well-developed -eyes. In four species there are eyes -which are evidently degenerating. If we compare, -for instance, the structure of the eye of <i>Serolis schythei</i>, -a species found in shallow water ranging from 4 to -70 fathoms, with the eyes of <i>Serolis bromleyana</i>, a -<span class='pageno' id='Page_128'>128</span>species living in deep water ranging from 400 to 1,975 -fathoms, we cannot fail to see that the latter are -undergoing a process of degeneration; the retinulæ -and pigment being absent, and nothing left of the -complicated structure of the Isopod eye but the -remnants of the crystalline cones and corneal facets -(see figs. 4 and 5, p. <a href='#Page_74'>74</a>).</p> - -<p class='c007'>Taking the genus <i>Serolis</i> alone, it has been -said ‘that in all the shallow-water forms the eye -is relatively small but very conspicuous from the -abundant deposition of pigment; in all the deep-sea -forms, with the exception of <i>S. gracilis</i>, where the eye -seems to be disappearing, it is relatively larger but -not so conspicuous, owing to the fact that little or no -pigment is present.’</p> - -<p class='c007'>In many groups of animals it has been shown -that some of the deep-sea species are relatively much -larger in size than the shallow-water species, and -that others, more rarely, are much smaller, the -abysmal fauna reminding us in this respect of the -characters of the alpine flora.</p> - -<p class='c007'>The Isopoda show many examples of this largeness -in size, thus <i>Bathynomus giganteus</i>, dredged by -Professor Agassiz off the Tortugas at a depth of over -900 fathoms, reaches the enormous size, for an Isopod, -<span class='pageno' id='Page_129'>129</span>of 9 inches (fig. <a href='#fig15'>15</a>). <i>Stenetrium haswelli</i>, again, is -larger than any of the shallow-water species of the -genus, and the same remark applies to the deep-sea -species of the genus <i>Ichnosoma</i>, while <i>Iolanthe -acanthonotus</i>, from a depth of nearly 2,000 fathoms, -is considerably larger than most of the shallow-water -Asellidæ.</p> - -<p class='c007'>There is another very common character of deep-sea -Crustacea that is also well exemplified in the -group of the Isopods, and that is the extraordinary -length and number of the spines covering the body.</p> - -<p class='c007'>I have already referred to this character in the -supposed deep-sea Copepod <i>Pontostratiotes abyssicola</i>, -and I shall have again to refer to it in treating of the -Decapoda and other groups of the Crustacea.</p> - -<p class='c007'>Besides its enormous size <i>Bathynomus</i> possesses -some other characters that may be correlated with -its deep-sea environment. The respiratory organs are -quite different from those of other Isopods; instead -of being borne by the abdominal appendages, they -are in the form of branched outgrowths from the -body-wall containing numerous blood-lacunæ, and -the appendages simply act as opercula to cover and -protect them. The eyes of the Bathynomus too are -remarkably well developed, each one bearing 4,000 -<span class='pageno' id='Page_130'>130</span>facets, and they are directed not dorsally as in the -Cymothoadæ, but ventrally. The cause of these -curious modifications of structure in Bathynomus is -by no means clear, but it is quite probable that they -are connected with the conditions of pressure and light -in the deep sea. It is a remarkable fact that the other -deep-sea Isopods do not exhibit precisely these modifications, -and it might be supposed that the same -causes would produce the same or similar effects on -the structure of animals belonging to the same order. -That is perfectly true, but we cannot yet determine -how long ago any one species has taken to a deep-sea -life, or what length of time, in other words, these -conditions have been at work in modifying the -structure of the organism. A recent immigrant into -the abyss will naturally exhibit closer affinities with -its shallow-water allies than those that have dwelt in -the region since secondary or tertiary times. If we -take this into consideration we should expect to find -considerable differences occurring between deep-sea -species of the same order, which is precisely what we -do find.</p> - -<div class='figcenter id003'> -<span class='pageno' id='Page_131'>131</span> -<img src='images/fig_015.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 15<a id='fig15'></a>.</span>—<i>Bathynomus giganteus.</i> From a depth of 1,740 metres. (From Filhol.)</p> -</div> -</div> - -<p class='c007'><span class='pageno' id='Page_132'>132</span>Concerning the Cirripedia, that curious group -of profoundly modified Crustacea that includes the -barnacles and acorn shells, Dr. Hoek writes in the -‘Challenger’ monograph:—</p> - -<p class='c007'>‘Though unquestionably by far the greater part -of the known Cirripedia are shallow-water species, -and though some of the species are capable of living -at a considerable variety of depths, as, for instance, -<i>Scalpellum stroemii</i>, yet it must be granted that the -number of true deep-sea species of Cirripedia is very -considerable.’ Only two genera, however, occur in -depths of over 1,000 fathoms, and these—<i>Scalpellum</i> -and <i>Verruca</i>—occur also as fossils in secondary and -tertiary deposits. The oldest of all fossil cirripedes, -however, namely, <i>Pollicipes</i>, never occurs, at the -present day, in deep water, but is purely littoral or -neritic in habit. But what is perhaps more interesting -still is the fact, that, when we come to compare -the living and the fossil species, we find that in the -one genus (<i>Scalpellum</i>) the deep-sea forms have preserved -the more archaic characters, and in the other -(<i>Pollicipes</i>) the shallow-water forms.</p> - -<p class='c007'>Here then we are presented with a veritable -puzzle for which we can at present frame no manner -of answer. Pollicipes on the one hand—like Lingula -among the brachiopods—has been able to maintain -itself almost unchanged amid the tremendous struggle -<span class='pageno' id='Page_133'>133</span>for life of the shallow water of the tropics ever since -the Lower Oolite epoch; while Scalpellum, on the -other hand, has either become profoundly modified, -or been driven into the abysmal depths of the ocean.</p> - -<p class='c007'>The group of the Thoracostraca, or stalk-eyed -Crustacea, including lobsters, crabs, hermit crabs, -prawns, and shrimps, is well represented in the deep -sea. Most of them are characterised by being quite -blind (in many cases even the eye-stalks are obliterated), -by being protected with a dense covering of -spines, by the thinness of their shells, and by their -bright red or carmine colour.</p> - -<p class='c007'>The order Stomatopoda is almost entirely confined -to the shallow waters of the tropical or temperate -shores. Not a single species is known to inhabit the -deep sea, and only a very few specimens have been -captured in more than a few fathoms of water.</p> - -<p class='c007'>The Schizopoda, however, present us with many -curious abysmal forms. Most of the genera of this -order belong to the pelagic plankton, and many of -them are known to possess the power of emitting a -very strong phosphorescent light. Several genera, -however, such as <i>Gnathophausia</i>, <i>Chlaraspis</i>, <i>Eucopia</i>, -<i>Bentheuphausia</i>, &c., never seem to leave the great -depths of the ocean, and nearly all of these genera -<span class='pageno' id='Page_134'>134</span>are distinguished by being quite blind or possessing -very much reduced or rudimentary eyes.</p> - -<div class='figcenter id001'> -<img src='images/fig_016.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 16<a id='fig16'></a>.</span>—<i>Euphausia latifrons</i>, from the surface of the sea. (After Sars.)</p> -</div> -</div> - -<div class='figcenter id001'> -<img src='images/fig_017.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 17<a id='fig17'></a>.</span>—<i>Bentheuphausia amblyops</i>, from 1,000 fathoms. (After Sars.)</p> -</div> -</div> - -<p class='c007'>If we compare, for example, the pelagic <i>Euphausia -latifrons</i> (fig. <a href='#fig16'>16</a>) with the nearly allied but abysmal -<i>Bentheuphausia amblyops</i> (fig. <a href='#fig17'>17</a>), the difference in -this respect between a Schizopod living in the sunlight -and one living in the darkness of the deep-sea -is very apparent.</p> - -<p class='c007'><span class='pageno' id='Page_135'>135</span>The pelagic Schizopoda are usually quite pale and -transparent; the deep-sea forms on the other hand -are frequently if not invariably of a bright red colour, -as is the case with many other deep-sea Crustacea to -which reference will be made later on.</p> - -<p class='c007'>Passing on to the group of the Decapoda, we find -that the most interesting of all the abysmal cray-fish -is the family of the Eryonidæ; indeed, in some -respects the discovery of these curious forms may be -reckoned among the most valuable results of the -‘Challenger’ Expedition. They are characterised by -the dorsal depression of the anterior part of the cephalothorax, -the absence of a rostrum, and the absence -or very rudimentary condition of the eyes (fig. <a href='#fig18'>18</a>).</p> - -<p class='c007'>Their nearest relations seem to be certain genera -of Crustacea that are found in jurassic strata, in the -lias, and more particularly in the lithographic slates -of Solenhofen.</p> - -<p class='c007'>They have a very wide bathymetrical range extending -from a depth of 250 fathoms (<i>Polycheles -crucifera</i>) to a depth of 2,000 fathoms (<i>Willemoesia</i>).</p> - -<div class='figcenter id006'> -<span class='pageno' id='Page_136'>136</span> -<img src='images/fig_018.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 18<a id='fig18'></a>.</span>—<i>Polycheles baccata</i>, one of the Eryonidæ. The eyes and eye-stalks are absent, and the margin and sides of the carapace armed with spines. (After Spence Bate.)</p> -</div> -</div> - -<p class='c007'>But there are many other curious forms of the -macrurous crustacea that deserve a passing mention. -The graceful <i>Nematocarcinus gracilipes</i>, distinguished by the extraordinary length of the antennæ -and last four pairs of legs, these appendages being -<span class='pageno' id='Page_137'>137</span>three or four times the length of the body, is by -no means rarely met with in depths of over 400 -fathoms.</p> - -<p class='c007'>The genus <i>Glyphus</i> captured by the ‘Talisman’ is -remarkable for the development of a peculiar pouchlike -arrangement on the abdomen for the protection of -the larvæ during the younger stages of their existence.</p> - -<p class='c007'>The proof of the existence of a peculiar cray-fish, -<i>Thaumastocheles zaleuca</i>, at a depth of 450 fathoms, -was one of the most important contributions to -carcinology made by the ‘Challenger’ Expedition. -The chelæ of this remarkable form are of great but -unequal length and armed with long tooth-like spines -giving it an appearance not unlike that of the jaws -of some carnivorous fish. The shell is soft and the -abdomen broad and flattened. There are no eyes -nor even eye-stalks, but ‘in front of the carapace,’ as -Sir Wyville Thomson remarks, ‘between the anterior -and upper edge and the insertions of the antennæ, -in the position of the eyes in such forms as <i>Astacus -fluviatilis</i>, there are two round vacant spaces, which -look as if the eye-stalks and eyes had been carefully -extirpated and the space they occupied closed with -a chitinous membrane.’ The deep-sea prawn, <i>Psalidopus</i>, -recently taken in 500 fathoms of water by the -<span class='pageno' id='Page_138'>138</span>‘Investigator,’ affords us an example of a common -bathybial character, the whole body being covered with -an extraordinary array of sharp needle-like spines.</p> - -<p class='c007'>Among the crabs many curious forms have been -found in deep water extending down to depths of -over 2,500 fathoms. They are nearly all characterised -by blindness and a remarkable development of tooth-like -spines covering the carapace and limbs.</p> - -<p class='c007'>The remarkable <i>Lithodes ferox</i>, from a depth of -from 450 to 800 fathoms, is perhaps the most perfectly -armed crab—in the way of spines—that exists. -Every part of the body and limbs is so covered with -spines that one has to be extremely careful in handling -even a dead specimen.</p> - -<p class='c007'>This is only one of the many examples that -might be given to illustrate this curious feature of -the deep-sea Crustacea. Among the crabs alone we -have such forms as <i>Galathodes Antonii</i>, <i>Pachygaster -formosus</i>, <i>Dicranodromia mahyeuxii</i> covered with a -fierce armature of spines or bristles; but there are -nevertheless some species in which this character is -not particularly noticeable, and in these we usually -find some other protection against their enemies. -An interesting example of this has been described -by A. Agassiz in a crab allied to the Maiadæ, -<span class='pageno' id='Page_139'>139</span>‘in which the dorsal face appears like a bit of -muddy area covered by corals, with a huge white arm -resembling a fragment of an Isis-like gorgonian.’ -It is evident that this is a case in which the animal -is protected by its resemblance to the surroundings.</p> - -<p class='c007'>The hermit crabs of the abyss, too, are not usually -characterised by any very great development of -spines. They find their protection in the shells they -inhabit. Some of the deep-sea hermit crabs carry -about with them on their shells a sea anemone, as we -find to be frequently the case among the shallow-water -species. <i>Pagurus abyssorum</i>, from a depth of 3,000 -fathoms, is an example of this.</p> - -<p class='c007'>In cases where there is a scarcity of gasteropod -shells the hermit crabs are obliged to find some -other form of protection for their bodies. The ‘Blake’ -found in the West Indies a hermit crab that had -formed for itself a case of tightly compressed sand, -and another curious form, named <i>Xylopagurus rectus</i>, -makes its home in pieces of bamboo or in the holes -in lumps of water-logged wood.</p> - -<p class='c007'>The last group of the Arthropoda we need refer -to is that of the Pycnogonida, those curious creatures -seemingly made up entirely of legs, and by some -<span class='pageno' id='Page_140'>140</span>naturalists considered to be related to the Crustacea -and by others to the scorpions and spiders.</p> - -<p class='c007'>Like the Brachiopoda the Pycnogonida are not -usually found in greater depths than 500 fathoms. -Out of the twenty-seven known genera, only five -extend into the abyss, and not one of these can be -called a true deep-sea genus.</p> - -<p class='c007'>There are three genera, <i>Nymphon</i>, <i>Collosendeis</i>, -and <i>Phoxichilidium</i>, that show a very wide distribution -over the floor of the ocean, and are capable of -existing at the greatest depths, and of these the -species of the genus Nymphon have a truly remarkable -range extending from the shore to a depth of -2,225 fathoms.</p> - -<p class='c007'>‘As a rule,’ says Hoek, ‘the deep-sea species are -slender, the legs very long and brittle, and the surface -of the body smooth.’ They have further, either -no eyes at all or rudimentary eyes without pigment, -and in many cases—as, for example, <i>Collosendeis</i>—they -are distinguished for reaching to a gigantic size -compared with their shallow-water relatives.</p> - -<p class='c007'>The Tunicata is the group of animals that -includes all those curious vegetable-like organisms -found upon our coasts that are familiarly known as -sea-squirts, or Ascidians, besides the salps, pyrosomas, -and the microscopic appendicularias of the pelagic -plankton.</p> - -<div class='figcenter id001'> -<span class='pageno' id='Page_141'>141</span> -<img src='images/fig_019.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 19<a id='fig19'></a>.</span>—<i>Collosendeis arcuatus</i>, from a depth of 1,500 metres. (After Filhol.)</p> -</div> -</div> - -<p class='c007'><span class='pageno' id='Page_142'>142</span>Notwithstanding the apparent simplicity of their -adult structure, naturalists are now agreed that they -must be removed from the Mollusca, with which they -have hitherto been most frequently associated, and -placed in the group of the Vertebrata. It is the -study of embryology that has led to this unexpected -conclusion, for we find, when we study the larval forms, -that they possess both a notochord and gill-slits, two -features that are characteristic of the group of the -Vertebrata.</p> - -<p class='c007'>The species of the group Perennichordata, which -includes all those Tunicates that possess a notochord -persistent through life, are chiefly pelagic in -habit, the little creatures, rarely more than two or -three millimetres in length, swimming or drifting -about with the sagittas, copepods, ctenophores, and -medusæ that compose the pelagic plankton. Fol has -recently described a gigantic form belonging to this -group, reaching a size of thirty millimetres in length, -called <i>Megalocercus abyssorum</i>, which he dredged -from a depth of 492 fathoms; and other species have -been recorded down to a depth of 710 fathoms in the -Mediterranean Sea.</p> - -<p class='c007'><span class='pageno' id='Page_143'>143</span>Among the simple Ascidians we find no family -that is peculiar to deep water; but the Cynthiidæ and -Ascidiidæ both contain genera that are abysmal, and -the Molgulidæ have one species, <i>Molgula pyriformis</i>, -that extends into the abysmal zone to a depth of 600 -fathoms.</p> - -<p class='c007'>In the genus <i>Culeolus</i> and in <i>Fungulus cinereus</i> -and <i>Bathyoncus</i>, all deep-water Ascidians, there is a -very curious modification of the branchial sac, the -stigmata being apparently not formed, in consequence -of the suppression of the fine inter-stigmatic vessels. -This peculiar feature is only found in the deep-sea -simple Ascidians and, as we shall see presently, in one -species of the deep sea compound Ascidians, but it is -not apparently an essential character of those living -in the abysmal zone, notwithstanding the fact that -it is found in such widely separated genera; for -<i>Corynascidia</i>, <i>Abyssascidia</i>, and <i>Hypobythius</i>, living in -depths lying between 2,000 and 3,000 fathoms below -the surface, have branchial sacs of the ordinary type. -Professor Herdman is of opinion that this simple form -of branchial sac is not a primitive form, but most -probably a modification of a more complicated type.</p> - -<p class='c007'>In <i>Culeolus Murrayi</i> there is a remarkably abundant -supply of blood-vessels to the tunic, and these -<span class='pageno' id='Page_144'>144</span>send special branches to a number of small papilliform -processes on its outer surface. This system -of highly vascular processes probably constitutes, as -Professor Herdman suggests, an additional or complementary -respiratory apparatus. All these modifications -of the branchial system are of particular -interest, for we find so many instances of a similar -kind among the inhabitants of very deep water. -I need only refer here to the modifications of this -system in the Isopod <i>Bathynomus</i> already referred -to (p. <a href='#Page_129'>129</a>), and to the reduction in the number of -the gills of many of the deep-sea fishes. Why there -should be such modifications is a question upon which -the physical and natural history investigations of the -conditions of life in the great depths of the ocean at -present throw no light.</p> - -<p class='c007'>In a previous chapter I have referred to the fact -that many of the bathybial animals are characterised -by being stalked. Among the simple Ascidia we -find many examples of stalked kinds living in deep -water, such as <i>Culeolus</i> and <i>Fungulus</i>, but also several -exceptions, such as <i>Bathyoncus</i>, <i>Styela bythii</i>, and -<i>Abyssascidia</i>, that are sessile. It is a noteworthy fact, -however, that the genus that has the most deep-sea -species—namely, <i>Culeolus</i>—is a genus that is provided -with a very long stalk. Furthermore, the only known -stalked forms of the very large family Ascidiidæ are -the abysmal genera <i>Corynascidia</i> and <i>Hypobythius</i>.</p> - -<div class='figcenter id006'> -<span class='pageno' id='Page_145'>145</span> -<img src='images/fig_020.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 20<a id='fig20'></a>.</span>—<i>Hypobythius calycodes.</i> <span class='fss'>G</span>, nerve ganglion; <span class='fss'>H</span>, heart; <span class='fss'>M</span>, the position of the atriopore. The large opening on the upper side is the mouth. (From a drawing by Professor Moseley in Herdman’s ‘Tunicata of the “Challenger” Expedition.’)</p> -</div> -</div> - -<p class='c007'><span class='pageno' id='Page_146'>146</span>The most remarkable character of the genus -<i>Hypobythius</i> is the simple condition of its branchial -sac, reminding one of the structure of this organ in the -shallow-water genus <i>Clavelina</i>. ‘There are no folds -and there are no internal bars,’ to quote the description -given by Professor Herdman; ‘only a single -system of vessels can be recognised, branching and -anastomosing so as to form a close network, the small -rounded meshes of which are the stigmata. The -tentacles and dorsal lamina cannot be made out.’</p> - -<p class='c007'>Among the compound Ascidians only four families -extend into the abysmal zone, namely, the Botryllidæ, -Polyclinidæ, Didemnidæ, and Cœlocormidæ, and of -these only one species, <i>Pharyngodictyon mirabile</i>, of -the family Polyclinidæ, extends into water of greater -depth than 1,000 fathoms. In <i>Pharyngodictyon</i> we -find the same curious simplification of the branchial -sac that we have just referred to in the genera of -simple Ascidians, <i>Culeolus</i>, <i>Fungulus</i>, and <i>Bathyoncus</i>. -<i>Cœlocormus Huxleyi</i> from a depth of 600 fathoms is -a very peculiar form and the type of a separate family, -the Cœlocormidæ.</p> - -<p class='c007'><span class='pageno' id='Page_147'>147</span>The free-swimming Tunicata included in the -group <i>Ascidiæ salpiformes</i>, which contains the genus -<i>Pyrosoma</i>, and the order Thaliacea containing the -salps, are in all probability mainly confined to the -surface waters. A few specimens of <i>Pyrosoma</i> were -captured by the ‘Challenger’ dredges which came up -from very deep water, but it is doubtful at what point -in the journey to the surface the specimens entered -the net.</p> - -<p class='c007'>The most remarkable form of free-swimming -Tunicate that has come to light is <i>Octacnemus bythius</i>, -a form that is probably allied to <i>Salpa</i>. It was -found twice, once in the dredge that came from a -depth of 1,070 fathoms, and once from 2,160 fathoms. -The tunic of the animal is gelatinous and hyaline, -but the most important feature it possesses is an -imperforate membrane separating the branchial sac -from the peribranchial cavity. Octacnemus, in other -words, possesses no true stigmata, these structures -being represented only by little pits in the walls -of the branchial sac. This curious and extremely -interesting modification of the respiratory organs -points very strongly to the conclusion that Octacnemus -is truly a deep-sea animal.</p> - -<div class='chapter'> - <span class='pageno' id='Page_148'>148</span> - <h2 class='c005'>CHAPTER VIII<br /> <span class='large'>THE FISH OF THE DEEP SEA</span></h2> -</div> - -<p class='c006'>Of all the groups of animals that constitute the -deep-sea fauna, the fish show the greatest number -of peculiarly abysmal characters. Being much -more highly differentiated than the invertebrates, -they possess more organs liable to undergo modifications -of colour, size, and structure, and consequently -we are able to point to a great many more -features characteristic of deep-sea fish than we can -do in any other group of animals.</p> - -<p class='c007'>The first point that calls for remark in the consideration -of the fish fauna of the deep sea is the -almost entire absence of ancient and primitive types. -The Elasmobranchii, including the Sharks, Rays, and -Chimæra, constituting the order that from anatomical -embryological grounds is always regarded by naturalists -as the most primitive order of this class, is -represented in very deep water by only one species. -<span class='pageno' id='Page_149'>149</span><i>Raia hyperborea</i> and <i>Chimæra monstrosa</i>, it is true, -just enter into the abysmal zone, but <i>Chimæra affinis</i> -is the only Elasmobranch that extends to depths of -over 1,000 fathoms.</p> - -<p class='c007'>The Ganoidei too, the order that in palæozoic -and mesozoic times was so rich in genera and species, -is entirely absent from the abysmal zone, not a single -representative having been found at any time by any -of the deep-sea expeditions.</p> - -<p class='c007'>The Dipnoi, that remarkable order including the -three fresh-water genera, <i>Ceratodus</i> from Australia, -<i>Lepidosiren</i> from Brazil, and <i>Protopterus</i> from West -Africa, has no representative and no ally in the deep -waters of the ocean.</p> - -<p class='c007'>The fishes of the deep sea, in fact, with only one -or two exceptions, all belong to the Order Teleostei, -the most modern and most highly differentiated order -of the class, the families that are most fully represented -being the Macruridæ and then the Ophidiidæ -and Gadidæ, and the Berycidæ.</p> - -<p class='c007'>At the limits of the katantic and abysmal zones, a -large number of families of Teleosteans entirely disappear, -and as we approach the deepest parts of the -ocean, the number of fish that are found is considerably -reduced. As Dr. Günther very wisely remarks, -<span class='pageno' id='Page_150'>150</span>‘this diminution in the number may be due to the -difficulty of capturing fishes at great depths, a difficulty -which increases in proportion to the depths at -which the dredge is worked. But it must also be -regarded as evidence of the actually diminished variety -of fishes.’</p> - -<p class='c007'>It may be interesting to the reader to give Dr. -Günther’s table of the number of species found at -different depths, as it shows, among other things, the -marked change that occurs in the character of the -fauna in passing from the katantic to the abysmal -zone.</p> - -<table class='table1' summary=''> - <tr> - <td class='c009'>Between</td> - <td class='c015'>100–300</td> - <td class='c015'>fathoms,</td> - <td class='c017'>232 species</td> - </tr> - <tr> - <td class='c009'>Between</td> - <td class='c015'>300–500</td> - <td class='c015'>fathoms,</td> - <td class='c017'>142 species</td> - </tr> - <tr> - <td class='c009'>Between</td> - <td class='c015'>500–700</td> - <td class='c015'>fathoms,</td> - <td class='c017'>76 species</td> - </tr> - <tr> - <td class='c009'>Between</td> - <td class='c015'>700–1,500</td> - <td class='c015'>fathoms,</td> - <td class='c017'>56 species</td> - </tr> - <tr> - <td class='c009'>Between</td> - <td class='c015'>1,500–2,000</td> - <td class='c015'>fathoms,</td> - <td class='c017'>24 species</td> - </tr> - <tr> - <td class='c009'>Between</td> - <td class='c015'>2,000–2,900</td> - <td class='c015'>fathoms,</td> - <td class='c017'>23 species</td> - </tr> -</table> - -<p class='c007'>As regards the general character presented by -the deep-sea fishes, I have already pointed out in the -chapter dealing with the general characters of the -deep-sea fauna, the peculiarities in the size of the eyes, -the colours and markings of the body, and the texture -of the bones and muscles. There are, however, a few -more characters of which mention must be made.</p> - -<p class='c007'>Notwithstanding the fact that all the abysmal -fishes<a id='t150'></a> are carnivorous and must consequently be -<span class='pageno' id='Page_151'>151</span>capable—in the great number of cases—of rapid and -vigorous movement, the muscles of the trunk and -tail are usually thin, and the fascicles loosely connected -with one another.</p> - -<p class='c007'>Deep-sea fish are not characterised by an absence -of the swimming bladder. This organ occurs just as -frequently and in the same families as in the shallow-water -fauna, but we do not know whether it possesses -any special peculiarities or not, as it is usually so -ruptured and destroyed by the change of pressure -it undergoes in being brought to the surface, that it -is impossible to make any thoroughly accurate investigation -of its anatomy and relations.</p> - -<p class='c007'>The extraordinary development of glands in the -skin which secrete mucus, and the presence in many -forms of very highly specialised organs for emitting -phosphorescent light, are characters of the deep-sea fish -fauna, to which I have referred in a previous chapter.</p> - -<p class='c007'>As with the Tunicates, some of the Crustacea -and other groups, the fish of the abysmal zone show -curious modifications of the respiratory system. The -gill laminæ of these animals are not only reduced -in number, but appear to be short and shrunken. -It is possible, of course, that during life they may -end in fine delicate points which are broken -<span class='pageno' id='Page_152'>152</span>off or ruptured during their capture, but still the -horny rods that support them are shorter than they -are in shallow-water forms, and the general evidence -of their structure tends to show that they have -undergone profound modifications in the change to -the conditions of deep-sea life.</p> - -<p class='c007'>An extremely common and almost general -character of deep-sea fishes is the black coloration -of some of the body cavities; this is limited to the -pharynx in many of the fishes that live about the -hundred fathoms limit, but the colour is more intense -and spread all over the oral, branchial, and peritoneal -cavities in typical deep-sea forms. It may seem very -difficult at first to account for this remarkable development -of black pigment in parts of the body that -are not usually, and, in some cases, cannot at any -time be exposed to view. It is obvious that it cannot -be functional as a hiding colour, either in offence -or defence. But it is quite possible that it is due to -some modification of the function of excretion. It is -well known that in many cases of disease or injury to -the kidneys in vertebrates, the colour of the skin is -affected, and every one recognises now the fact that in -many invertebrates the colour of the skin is greatly dependent -upon the function of the secretion of the urates.</p> - -<p class='c007'><span class='pageno' id='Page_153'>153</span>It would at least be interesting to know if this -dark coloration of the mucous membranes is in any -way correlated with any modification of the structure -or function of the kidneys. At present we have no -recorded observations on this point, but it is to be -hoped that, when we have a sufficient number of -specimens brought home from the deep water, a -systematic investigation of this subject will be made.</p> - -<p class='c007'>Lastly, it should be pointed out that our knowledge -of the abysmal fauna has not, at present, brought -to light any evidence that the fish are of an extraordinarily -large size. In many groups of animals, as -I have frequently pointed out in the last few chapters, -the large and gigantic species or specimens are only -found in the abyss. This may also be the case with -fishes, but we have no evidence that it is so. The -only methods that have been used at present for the -investigation of the fauna living on or near the -floor of the deep oceans, are not of a kind to lead -to the capture of really large fish. That they may -exist is highly probable, but all that we know at -present is, that the fish with which we are acquainted -living at great depths are not in any way remarkable -for their great size.</p> - -<p class='c007'>Of the only two Elasmobranchs, one, namely <i>Raia -<span class='pageno' id='Page_154'>154</span>hyperborea</i>, has been found in water extending from -400 to 608 fathoms in depth. Only four specimens -have yet been taken, one by the Norwegian expedition -off Spitzbergen and three by the ‘Knight -Errant’ off the northern coasts of Scotland. It is -interesting to find that this, the only deep-sea species -of the Rays, shows some striking peculiarities. ‘The -teeth are remarkably slender,’ says Günther, ‘small, -irregularly and widely set, different from those of other -British Rays. In young specimens at any rate those -of the male do not differ from those of the female. -The mucous membrane behind the upper jaw forms -a pad with a lobulated surface. The mucous cavities -of the head are extremely wide, and finally the accessory -copulatory organs have a spongy appearance, -and are flexible, the cartilage by which they are supported -being a simple slender rod.’</p> - -<p class='c007'>The other Elasmobranch, that extends into very -deep water, is <i>Chimæra affinis</i>, a species which can -hardly be distinguished from the better known -<i>Chimæra monstrosa</i>, a fish that itself very frequently -wanders within the limits of the abysmal zone.</p> - -<p class='c007'>Among the Teleostei, the family Berycidæ has -several representatives in the deep water. They are -small fish rarely exceeding four inches in length, with -<span class='pageno' id='Page_155'>155</span>large heavy heads, with functional but small eyes, -and an abundant supply of large mucous glands on -the skin.</p> - -<p class='c007'><i>Melamphaes beanii</i>, belonging to this family, -has been captured at the enormous depth of 2,949 -fathoms.</p> - -<p class='c007'><i>Bathydraco antarcticus</i>, belonging to the family -Trachinidæ, from a depth of 1,260 fathoms, is an -example of a true abysmal fish possessing very large -eyes.</p> - -<p class='c007'>The Pediculati, the family of the anglers, is represented -at depths of over 2,000 fathoms by the -interesting form <i>Melanocetus Murrayi</i>. The eyes are -very small indeed, the mouth huge and armed with -long uneven rasp-like teeth. At the end of the fishing-rod -tentacle hanging over the mouth, there is an -organ that has been supposed to be capable of emitting -a phosphorescent light. This curious modification of -the red worm-like bait of the common shallow-water -angler into a will-o-the-wisp lantern attracting little -fishes to their destruction in the deadly jaws of the -<i>Melanocetus</i> is one of the most interesting adaptations -that have been brought to light by our study of the -deep-sea fauna.</p> - -<p class='c007'>Several species of the family Lycodidæ occur in -<span class='pageno' id='Page_156'>156</span>the abysmal zone, but they do not possess any -features that call for special mention in this place.</p> - -<div class='figcenter id001'> -<img src='images/fig_021.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 21<a id='fig21'></a>.</span>—<i>Melanocetus Murrayi</i>, 1,850–2,450 fathoms. (After Günther.)</p> -</div> -</div> - -<p class='c007'>The family Ophidiidæ contributes very largely to -the fish fauna of the abyss. Some of the deep-water -genera, such as <i>Neobythites</i>, have a wide bathymetrical -distribution extending from 100 fathoms to -depths of over 2,000 fathoms, but others, such as -<i>Bathyonus</i>, <i>Typhonus</i>, and <i>Aphyonus</i>, only occur in -depths of over 1,000 fathoms.</p> - -<p class='c007'>The body is usually elongate and slender, ending -in a pointed tail, the head large and heavy, and the -eyes, in the genera confined to the abysmal zone, -usually so far degenerated that they are not visible at -all from the outside.</p> - -<p class='c007'>The Macruridæ form a family that contributes -<span class='pageno' id='Page_157'>157</span>very largely to the deep-sea fauna; no fewer than -twenty-six different species are known to occur -within the limits of the abysmal zone. Not only -do the Macruridæ contribute a large number of -different species, but they probably occur, in some -districts at any rate, in vast numbers.</p> - -<p class='c007'>During the voyage of the ‘Talisman,’ for example, -the French naturalists caught in one haul of the -dredge off the coast of Morocco in 500 fathoms of -water no fewer than 134 fish, of which number 95 -belonged to the family Macruridæ.</p> - -<p class='c007'>They are usually small fish, measuring from a few -inches to two feet in length, with a body terminating -in a long compressed tapering tail and covered -with spiny, keeled, or striated scales.</p> - -<p class='c007'>The Pleuronectidæ or flat fish are not, as a rule, -found in the abysmal zone; one species, however, -<i>Pleuronectes cynoglossus</i>, was found by the American -ship ‘Blake’ to extend into 732 fathoms of water.</p> - -<p class='c007'>The families Sternoptychidæ and Scopelidæ are -of particular interest to us, as almost all the genera -they contain belong either to the pelagic or abysmal -zones, and lend support to the view enunciated by -Moseley, that the deep-sea fauna has, partly at any -rate, been derived from the fauna of the pelagic zone. -<span class='pageno' id='Page_158'>158</span>They are nearly all small slender fish with delicate -and frequently semi-transparent bodies, large gaping -mouths armed with numerous long irregular teeth, -and frequently provided upon the head and sides -of the trunk with rows of eye-like phosphorescent -organs.</p> - -<p class='c007'>These families, and others that have still to be -referred to, belong to the group of Teleostei that is -called Physostomi, the name referring to the open -communication that usually exists in all these families -between the swimming bladder and the alimentary -canal. It is a remarkable fact that in none of the -deep-sea representatives has this open communication -been discovered. It is true that many specimens are, -when examined, so lacerated by the diminution in -pressure as to render anatomical study a matter of -difficulty, but still a fair number of uninjured well-preserved -specimens have now been examined and -the duct has not been found.</p> - -<p class='c007'>Of the family Sternoptychidæ, <i>Gonostoma microdon</i> -has a most remarkable distribution. It has been -found at numerous stations in both the Pacific and -Atlantic Oceans at depths ranging from 500 to nearly -3,000 fathoms of water.</p> - -<p class='c007'>The Scopelidæ are represented by some very -<span class='pageno' id='Page_159'>159</span>extraordinary types. The genus <i>Bathypterois</i>, for -example, occurring in depths ranging from 500 to -2,500 fathoms, is characterised by the development of -enormously long pectoral fins to serve probably as -organs of touch. ‘The rays of the pectoral fin,’ says -Dr. Günther, ‘are much elongated. The ventral fins -abdominal, with the outer rays prolonged, eight-rayed.... -Gill rakers long.’ They are further -characterised by the absence of any true phosphorescent -organs and the smallness of their eyes.</p> - -<p class='c007'>There can be little doubt, I think, that in these -fishes the sense of touch or taste to a great extent -takes the place of the sense of sight in other Scopelids. -Not being provided with well-developed eyes -or phosphorescent organs to attract their prey, the -pectoral fins and the outer rays of the pelvic fins -have become elongated and provided with special -sense organs for searching for their food in the fine -mud of the floor of the ocean.</p> - -<p class='c007'>These long pectoral rays must have a very curious -appearance in the living fish. Mr. Murray observes: -‘When taken from the trawl they were always dead, -and the long pectoral rays were erected like an arch -over the head, requiring considerable pressure to -make them lie along the side of the body; when -<span class='pageno' id='Page_160'>160</span>erected they resembled the Pennatulids like -Umbellula.’ Filhol considers that when the fish is -progressing through the obscurity of the abyss it -probably carries these organs directed forward, seeking -with them in the mud for any worms or other -animals upon which it preys, or receiving through -them warning of the approach of an enemy from whom -it is necessary to make an immediate escape. One -of the most remarkable of the deep-sea fish is closely -related to Bathypterois, namely <i>Ipnops Murrayi</i>, -living in depths of over 1,000 fathoms. It is about -five inches long, of a yellowish brown colour, with an -elongated subcylindrical body covered with large thin -deciduous scales. There are no phosphorescent organs -of the ordinary type met with in the Scopelidæ, but -upon the upper surface of the head there is found a -pair of organs somewhat resembling the ordinary -eyes of fishes but devoid of retina and optic nerve, -that, from the researches of Moseley, seem to be undoubtedly -organs for emitting light. ‘The organs -are paired expanses, completely symmetrical in outline, -placed on either side of the median line of the -upper flattened surface of the head of the fish, extending -from a line a little posterior to the nasal -capsules nearly to a point above the posterior -<span class='pageno' id='Page_161'>161</span>extremity of the cranial cavity.’ They are covered -by the upper walls of the skull, which is extremely -thin and completely transparent in the region lying -over them. ‘They are membranous structures -0·4 mm. in thickness marked by hexagonal areas -about 0·04 mm. in diameter. When their surface is -viewed by reflected light the appearance is that of a -number of glistening white isolated short columns -standing up in relief from its basal membrane.’ Each -hexagonal column is composed of a number of transparent -rods disposed side by side at right angles to -the outer surface of the organ, with their bases applied -against the concave surface of a large hexagonal -pigment cell, one of which forms the basis of each -hexagonal column. It is still very doubtful what -are the true homologies of this extraordinary phosphorescent -organ, but Moseley was of opinion that, ‘on -the whole, it seems not unlikely that the remarkable -head organs of Ipnops may be regarded as highly -specialised and enormously enlarged representatives -of the phosphorescent organs on the heads of such -allied Scopelidæ as <i>Scopelus rafinesquii</i> and <i>Scopelus -metopoclampus</i>. It may be conceived that in <i>Ipnops</i> -the supra-nasal and sub-ocular phosphorescent organs -of these species on either side have united and -<span class='pageno' id='Page_162'>162</span>become one with the result of the total obliteration -of the eye.’</p> - -<p class='c007'>Most of the species of the genus <i>Scopelus</i> are -undoubtedly pelagic in habit, descending during the -day to depths of semi-darkness but rising at night -to the surface waters. It is not certain how many -of the known species occasionally or habitually dwell -in very deep water, but there seems to be no doubt -that two species at least—<i>S. macrolepidotus</i> and -<i>S. glacialis</i>—belong to the abysmal zone. Both -of these species were found in dredges that had been -at work in depths of over 1,000 fathoms and showed -signs when examined of having been brought from -the abyss.</p> - -<p class='c007'>The Stomiatidæ are almost entirely confined -to water from 450 to nearly 2,000 fathoms in -depth. They may be distinguished from the -Scopelidæ by the long hyoid barbel close to the -symphysis of the lower jaw, but like many of the -genera of that family they have wide gaping mouths -armed with a profusion of vicious looking teeth and -a series of luminous spots on the sides of the head -and body. (<i>See</i> <a href='#Frontispiece'>Frontispiece</a>.)</p> - -<p class='c007'>In <i>Eustomias obscurus</i>, found in depths of over -1,000 fathoms in the Atlantic by the ‘Talisman,’ the -<span class='pageno' id='Page_163'>163</span>barbel is provided with a terminal swelling, shaped -like a dumb-bell, which may be capable of emitting a -phosphorescent light and serve the animal as a lure -for the attraction of its prey. The genus <i>Malacosteus</i>, -too, presents us with some of the most remarkable -forms that are found in the abysmal zone. The -mouth is of enormous size and the integuments of -the abdomen present very definite longitudinal folds, -leaving no doubt that this fish is able, like several -others living in deep water, to swallow prey of an -enormous size.</p> - -<p class='c007'>But a perfectly unique structure in this fish ‘is -a thin cylindrical muscular band which connects -the back part of the mandibular symphysis with -the hyoid bone. It is probably the homologue of a -muscular band which, in other Stomiatids, stretches -on each side from the mandible to the side of the -hyoid, the two bands coalescing into an unpaired one in -<i>Malacosteus</i>. It is, in the present state of preservation, -much elongated, like a barbel, but during life it is -notably contractile, and serves to give to the extremity -of the mandible the requisite power of resistance -when the fish has seized its prey, as without such a -contrivance so long and slender a bone would yield to -the force of its struggling victim.’</p> - -<div class='figcenter id001'> -<span class='pageno' id='Page_164'>164</span> -<img src='images/fig_022.jpg' alt='' class='ig001' /> -<div class='ic001'> -<p><span class='sc'>Fig. 22<a id='fig22'></a>.</span>—<i>Saccopharynx ampullaceus</i>; a deep-sea eel, with the head of a large fish, which it has swallowed, showing through the thin integuments of the body. (From Günther.)</p> -</div> -</div> - -<p class='c007'>Belonging to the family of the Salmons we find -one genus <i>Bathylagus</i> that is undoubtedly an abysmal -form. Although there may be some doubt as to the -exact depth at which the specimens were captured, -the thinness of the bones, the enormous size of the -eyes, and other bathybial characters prove that they -must live in very deep water. Closely allied to the -salmon and the herrings is the family of the Alepocephalidæ, -a family that contributes several forms to -the fauna of the deep sea, but they do not possess -any characters that call for special comment. Their -vertical distribution varies between 345 and 2,150 -fathoms.</p> - -<p class='c007'>The family Halosauridæ contains five species all -confined to the abysmal zone. They have long bodies -tapering to a finely pointed tail, and the head is provided -<span class='pageno' id='Page_165'>165</span>with a snout that projects considerably in front -of the mouth.</p> - -<p class='c007'>Of the family of the Eels there are several representatives -in the deep sea. They are characterised -by a combination of true eel characters with -special modifications due to a bathybial existence. ‘To -enable them to seize upon prey more powerful than -themselves certain organs have undergone a degree -of specialisation, as is observed in bathybial members -of other families with a similar mode of life; the -jaws are exceedingly elongate and the whole gape, -the pharynx and stomach capable of enormous distension.’ -The head is very large, the eye very small -and the tail long and tapering (fig. <a href='#fig22'>22</a>).</p> - -<p class='c007'>The lessons we learn from the study of the fishes -of the deep sea are particularly instructive. It would -take far more space than can be afforded here to -fully illustrate all of the points that seem clear to us, -but I hope I have said sufficient to show that the -fish fauna is made up of genera and species belonging -to several widely separate families of the Teleostei; -that some of them show, in a very marked way, what -may be looked upon as peculiarly bathybial characters, -whilst others are but slightly modified from their -shallow-water representatives. These facts by themselves -<span class='pageno' id='Page_166'>166</span>lend support to the view that the fauna of -the deep sea has been derived from the fauna of -shallower water by successive migrations at different -periods of the world’s history. Those that exhibit in -a most marked degree the special bathybial characters -are probably those whose immigration took place -long ago, whilst those more closely related to shallow-water -forms are, comparatively speaking, recent -importations. The occurrence of Scopelidæ and -Sternoptychidæ in deep water suggests, as Moseley -pointed out many years ago, that the fauna is partly -derived from the pelagic plankton. But while these -points may seem clear to us, there are others that still -require much more investigation and consideration. -The whole question of the function and use of the -phosphorescent organs, the mucous glands, the -barbels and elongated fin rays, the mode of life, -the deposition of ova and their development, afford -problems which in the present state of our knowledge -must remain unsolved. Let us hope that in -the future there may be a new stimulus given to -deep-sea research, and these problems may be again -seriously studied and eventually solved.</p> - -<div class='chapter'> - <span class='pageno' id='Page_167'>167</span> - <h2 class='c005'>INDEX</h2> -</div> - -<ul class='index c001'> - <li class='c018'>Actiniaria, <a href='#Page_36'>36</a>, <a href='#Page_93'>93</a></li> - <li class='c018'>—— two remarkable genera of, <a href='#Page_15'>15</a></li> - <li class='c018'><i>Aegir</i>, <a href='#Page_15'>15</a></li> - <li class='c018'>Agassiz, A.,</li> - <li class='c018'>—— on colour of Cœlentera, <a href='#Page_65'>65</a></li> - <li class='c018'>—— on Echinoidea, <a href='#Page_101'>101</a>, <a href='#Page_103'>103</a></li> - <li class='c018'>Agassiz, L., on board the ‘Hassler,’ 12</li> - <li class='c018'>‘Albatross,’ American vessel, <a href='#Page_15'>15</a></li> - <li class='c018'>Alcyonaria, <a href='#Page_95'>95</a></li> - <li class='c018'>—— phosphorescence of, <a href='#Page_81'>81</a></li> - <li class='c018'>Amphipoda, <a href='#Page_124'>124</a></li> - <li class='c018'>Anemones</li> - <li class='c018'>—— of deep water, <a href='#Page_36'>36</a>, <a href='#Page_92'>92</a></li> - <li class='c018'>—— two remarkable genera of, <a href='#Page_15'>15</a></li> - <li class='c018'>Annelida, <a href='#Page_117'>117</a></li> - <li class='c018'>Ascidia compositæ, <a href='#Page_146'>146</a></li> - <li class='c018'>—— salpiformes, <a href='#Page_147'>147</a></li> - <li class='c018'>—— simplices, <a href='#Page_142'>142</a></li> - <li class='c018'>Asteroidea, <a href='#Page_104'>104</a></li> - <li class='c001'>Barriers of temperature, <a href='#Page_32'>32</a></li> - <li class='c018'><i>Bathynomus</i>, <a href='#Page_129'>129</a></li> - <li class='c018'>Beddard, F. E., on Isopoda, <a href='#Page_127'>127</a></li> - <li class='c018'>Benthos, <a href='#Page_53'>53</a></li> - <li class='c018'>Berycidæ, <a href='#Page_154'>154</a></li> - <li class='c018'>‘Blake,’ American vessel, <a href='#Page_12'>12</a></li> - <li class='c018'>Blue mud, <a href='#Page_42'>42</a></li> - <li class='c018'>Brachiopoda, <a href='#Page_115'>115</a></li> - <li class='c018'>Brachyura, <a href='#Page_138'>138</a></li> - <li class='c018'><i>Brisinga</i>, <a href='#Page_9'>9</a>, <a href='#Page_105'>105</a></li> - <li class='c018'>Buchanan’s experiment, <a href='#Page_19'>19</a></li> - <li class='c001'>Carpenter, P. H., on Crinoidea, <a href='#Page_100'>100</a></li> - <li class='c018'><i>Cephalodiscus</i>, <a href='#Page_113'>113</a></li> - <li class='c018'>Cephalopoda, <a href='#Page_120'>120</a></li> - <li class='c018'>‘Challenger,’ H.M.S., voyage of, <a href='#Page_12'>12</a></li> - <li class='c018'>Cirripedia, <a href='#Page_130'>130</a></li> - <li class='c018'>Cœlentera,</li> - <li class='c018'>—— colour of, <a href='#Page_65'>65</a></li> - <li class='c018'>—— of deep sea, <a href='#Page_91'>91</a></li> - <li class='c018'>Colour</li> - <li class='c018'>—— of the deep-sea fauna, <a href='#Page_59'>59</a>, <a href='#Page_66'>66</a></li> - <li class='c018'>—— of the deep-sea fish, <a href='#Page_60'>60</a></li> - <li class='c018'>Copepoda, <a href='#Page_124'>124</a></li> - <li class='c018'>Corals, <a href='#Page_94'>94</a></li> - <li class='c018'>Crinoidea, <a href='#Page_99'>99</a></li> - <li class='c018'>Crustacea, <a href='#Page_123'>123</a></li> - <li class='c018'>—— colour of, <a href='#Page_63'>63</a></li> - <li class='c001'>Darkness of the abyss, <a href='#Page_22'>22</a></li> - <li class='c018'>Diatom ooze, <a href='#Page_39'>39</a></li> - <li class='c018'>Dipnoi, <a href='#Page_149'>149</a></li> - <li class='c001'>Echinoderma, <a href='#Page_99'>99</a></li> - <li class='c018'>—— colour of, <a href='#Page_64'>64</a></li> - <li class='c018'>Echinoidea, <a href='#Page_101'>101</a></li> - <li class='c018'>Eels, <a href='#Page_165'>165</a></li> - <li class='c018'>Elasipoda, <a href='#Page_106'>106</a></li> - <li class='c018'>Elasmobranchii, <a href='#Page_148'>148</a>, <a href='#Page_153'>153</a></li> - <li class='c018'>Eryonidæ, <a href='#Page_135'>135</a></li> - <li class='c018'>Eyes of abysmal animals, <a href='#Page_67'>67</a></li> - <li class='c018'>—— of deep-sea crustacea, <a href='#Page_72'>72</a></li> - <li class='c018'><span class='pageno' id='Page_168'>168</span>—— of deep-sea fish, <a href='#Page_69'>69</a></li> - <li class='c018'>—— of deep-sea mollusca, <a href='#Page_71'>71</a></li> - <li class='c018'>—— of <i>Genityllis</i>, <a href='#Page_118'>118</a></li> - <li class='c018'>—— of <i>Neobythites</i>, <a href='#Page_69'>69</a></li> - <li class='c018'>—— of <i>Serolis</i>, <a href='#Page_73'>73</a></li> - <li class='c001'><i>Fenja</i>, <a href='#Page_15'>15</a></li> - <li class='c018'>‘Fish Hawk,’ American vessel, <a href='#Page_12'>12</a></li> - <li class='c018'>Fol and Sarasin’s experiments, <a href='#Page_25'>25</a></li> - <li class='c018'>Foraminifera, <a href='#Page_90'>90</a></li> - <li class='c018'>Forbes, on the probable existence of a deep-sea fauna, <a href='#Page_2'>2</a></li> - <li class='c018'>—— on zones of distribution, <a href='#Page_49'>49</a></li> - <li class='c001'>Ganoidei, <a href='#Page_149'>149</a></li> - <li class='c018'>Gasteropoda, <a href='#Page_119'>119</a></li> - <li class='c018'>Gephyrea, <a href='#Page_116'>116</a></li> - <li class='c018'>Gills of deep-sea fish, <a href='#Page_151'>151</a></li> - <li class='c018'>Globerigina ooze, discovery of, <a href='#Page_5'>5</a></li> - <li class='c018'>—— distribution and composition of, <a href='#Page_37'>37</a></li> - <li class='c018'>Green mud, <a href='#Page_42'>42</a></li> - <li class='c018'>Gunn, Dr., on the eyes of <i>Genityllis</i>, <a href='#Page_118'>118</a></li> - <li class='c018'>Günther, Dr., on deep-sea fish, <a href='#Page_150'>150</a></li> - <li class='c001'>Hall, Marshall, <a href='#Page_12'>12</a></li> - <li class='c018'>Halosauridæ, <a href='#Page_164'>164</a></li> - <li class='c018'>‘Hassler,’ American ship, <a href='#Page_12'>12</a></li> - <li class='c018'>Herdman, on Ascidians, <a href='#Page_143'>143</a>, <a href='#Page_146'>146</a></li> - <li class='c018'>Hermit crabs, <a href='#Page_139'>139</a></li> - <li class='c018'>Hoek, Dr., on Cirripedia, <a href='#Page_132'>132</a></li> - <li class='c018'>—— on Pycnogonida, <a href='#Page_140'>140</a></li> - <li class='c018'>Holothuridea, <a href='#Page_106'>106</a></li> - <li class='c018'>Hoyle, on Cephalopoda, <a href='#Page_120'>120</a></li> - <li class='c018'>Hydroids, <a href='#Page_92'>92</a></li> - <li class='c001'>‘Investigator,’ H.M.S., <a href='#Page_16'>16</a></li> - <li class='c018'><i>Ipnops Murrayi</i>, colour of, <a href='#Page_60'>60</a>, <a href='#Page_61'>61</a></li> - <li class='c018'><i>Ipnops Murrayi</i>, phosphorescent organs of, <a href='#Page_160'>160</a></li> - <li class='c018'>Isopoda, <a href='#Page_127'>127</a></li> - <li class='c001'>Katantic sub-zone, <a href='#Page_50'>50</a></li> - <li class='c018'>‘Knight Errant,’ H.M.S., <a href='#Page_12'>12</a></li> - <li class='c001'>Lamellibranchia, <a href='#Page_119'>119</a></li> - <li class='c018'>‘Lightning,’ H.M.S., <a href='#Page_8'>8</a>, <a href='#Page_9'>9</a></li> - <li class='c018'>Lime, scarcity of, in bones of bathybial fish, <a href='#Page_83'>83</a></li> - <li class='c018'>—— in shells of mollusca, <a href='#Page_83'>83</a></li> - <li class='c018'>Littoral sub-zone, <a href='#Page_49'>49</a></li> - <li class='c018'>Lycodidæ, <a href='#Page_155'>155</a></li> - <li class='c001'>Macrura, <a href='#Page_135'>135</a></li> - <li class='c018'>Macruridæ, <a href='#Page_156'>156</a></li> - <li class='c018'>Madreporaria, <a href='#Page_94'>94</a></li> - <li class='c018'>Medusæ, <a href='#Page_91'>91</a></li> - <li class='c018'>Mollusca, <a href='#Page_119'>119</a></li> - <li class='c018'>—— colour of, <a href='#Page_62'>62</a></li> - <li class='c018'>Moore, Capt., <a href='#Page_94'>94</a></li> - <li class='c018'>Moseley, H. N., on colour of Cœlentera, <a href='#Page_65'>65</a></li> - <li class='c018'>—— on phosphorescent organs of <i>Ipnops</i>, <a href='#Page_160'>160</a></li> - <li class='c018'>—— on the darkness of the abyss, <a href='#Page_22'>22</a></li> - <li class='c018'>—— on the phosphorescence of Alcyonarians, <a href='#Page_25'>25</a></li> - <li class='c018'>Murray, on <i>Bathypterois</i>, <a href='#Page_159'>159</a></li> - <li class='c001'>Nekton, <a href='#Page_53'>53</a></li> - <li class='c018'>Neritic zone, <a href='#Page_48'>48</a></li> - <li class='c018'>‘Norma,’ Mr. Hall’s yacht, <a href='#Page_12'>12</a></li> - <li class='c018'>Norske Nord-havns expedition, <a href='#Page_7'>7</a>, <a href='#Page_15'>15</a></li> - <li class='c001'>Ophidiidæ, <a href='#Page_156'>156</a></li> - <li class='c018'>Ostracoda, <a href='#Page_123'>123</a></li> - <li class='c001'>Packard, on the illumination of the abyss, <a href='#Page_23'>23</a></li> - <li class='c018'><span class='pageno' id='Page_169'>169</span>Pediculati, <a href='#Page_155'>155</a></li> - <li class='c018'>Pelagic zone, <a href='#Page_47'>47</a></li> - <li class='c018'>Pennatulidæ, <a href='#Page_96'>96</a></li> - <li class='c018'><i>Phoronis</i>, <a href='#Page_111'>111</a></li> - <li class='c018'>Phosphorescence of Alcyonarians, <a href='#Page_81'>81</a></li> - <li class='c018'>— of deep-sea Crustacea, <a href='#Page_80'>80</a></li> - <li class='c018'>— of Echinoderma, <a href='#Page_81'>81</a></li> - <li class='c018'>Phosphorescent light in the abyss, <a href='#Page_24'>24</a></li> - <li class='c018'>— organs of deep-sea fish, <a href='#Page_77'>77</a></li> - <li class='c018'>Pigment in mucous membranes of deep-sea fish, <a href='#Page_84'>84</a>, <a href='#Page_152'>152</a></li> - <li class='c018'>Plankton, <a href='#Page_52'>52</a></li> - <li class='c018'>Pleuronectidæ, <a href='#Page_157'>157</a></li> - <li class='c018'>Polar currents, <a href='#Page_30'>30</a>, <a href='#Page_33'>33</a></li> - <li class='c018'>Polychæta, <a href='#Page_118'>118</a></li> - <li class='c018'>‘Porcupine,’ H.M.S., <a href='#Page_8'>8</a>, <a href='#Page_9'>9</a></li> - <li class='c018'>Porifera, <a href='#Page_91'>91</a></li> - <li class='c018'>Pourtales, Count, <a href='#Page_10'>10</a></li> - <li class='c018'>Pressure in the abyss, <a href='#Page_19'>19</a></li> - <li class='c018'>Protozoa, <a href='#Page_88'>88</a></li> - <li class='c018'>Pteropod ooze, <a href='#Page_39'>39</a></li> - <li class='c018'>Pycnogonida, <a href='#Page_139'>139</a></li> - <li class='c001'>Radiolaria, <a href='#Page_89'>89</a></li> - <li class='c018'>Radiolarian ooze, <a href='#Page_39'>39</a></li> - <li class='c018'>Red mud, <a href='#Page_37'>37</a></li> - <li class='c018'>— — off the Brazilian coasts, <a href='#Page_42'>42</a></li> - <li class='c018'><i>Rhabdopleura</i>, <a href='#Page_111'>111</a></li> - <li class='c018'>Ross, Sir James, on the fauna of the deep sea, <a href='#Page_3'>3</a></li> - <li class='c001'>Salmonidæ, <a href='#Page_163'>163</a></li> - <li class='c018'>Sargasso sub-zone, <a href='#Page_48'>48</a></li> - <li class='c018'>Sars, <a href='#Page_6'>6</a>, <a href='#Page_9'>9</a>,</li> - <li class='c018'>— on Amphipoda, <a href='#Page_125'>125</a></li> - <li class='c018'>— on <i>Brisinga</i>, <a href='#Page_105'>105</a></li> - <li class='c018'>Schizopoda, <a href='#Page_133'>133</a></li> - <li class='c018'>Scopelidæ, <a href='#Page_158'>158</a></li> - <li class='c018'><i>Serolis</i>, <a href='#Page_127'>127</a></li> - <li class='c018'>Siphonophora, <a href='#Page_92'>92</a></li> - <li class='c018'>Size of deep-sea animals, <a href='#Page_85'>85</a></li> - <li class='c018'>— of fish, <a href='#Page_153'>153</a></li> - <li class='c018'>Smith, Mr., on Lamellibranchia, <a href='#Page_119'>119</a></li> - <li class='c018'>Spatangoids, <a href='#Page_101'>101</a></li> - <li class='c018'>Sponges, <a href='#Page_91'>91</a></li> - <li class='c018'>Stebbing, Rev. T. R., on Amphipoda, <a href='#Page_125'>125</a></li> - <li class='c018'>Sternoptychidæ, <a href='#Page_158'>158</a></li> - <li class='c018'>Stomatopoda, <a href='#Page_133'>133</a></li> - <li class='c018'>Stomiatidæ, <a href='#Page_162'>162</a></li> - <li class='c001'>‘Talisman,’ French vessel, <a href='#Page_12'>12</a></li> - <li class='c018'>Teleostei, <a href='#Page_149'>149</a>, <a href='#Page_154'>154</a></li> - <li class='c018'>Temperature of the abyss, <a href='#Page_28'>28</a></li> - <li class='c018'>Thomson, Sir Wyville, on <i>Pourtalesia</i>, <a href='#Page_10'>10</a></li> - <li class='c018'>— on <i>Thaumastocheles</i>, <a href='#Page_137'>137</a></li> - <li class='c018'>— on the darkness of the abyss, <a href='#Page_22'>22</a></li> - <li class='c018'>— on the phosphorescence of the sea, <a href='#Page_26'>26</a></li> - <li class='c018'>Thoracostraca, <a href='#Page_133'>133</a></li> - <li class='c018'>‘Travailleur,’ French vessel, <a href='#Page_12'>12</a></li> - <li class='c018'>‘Triton,’ H.M.S., <a href='#Page_12'>12</a></li> - <li class='c018'>Tunicata, <a href='#Page_140'>140</a></li> - <li class='c001'>Vegetable life, absence of, <a href='#Page_42'>42</a></li> - <li class='c018'>Verrill, on the illumination of the abyss, <a href='#Page_23'>23</a></li> - <li class='c018'>‘Vittor Pessani,’ Italian vessel, <a href='#Page_12'>12</a></li> - <li class='c018'>‘Vöringin,’ Norwegian vessel, <a href='#Page_14'>14</a></li> -</ul> - -<div class='pbb'> - <hr class='pb c002' /> -</div> -<div class='box'> - -<!-- <div class='section ph2'> --> -<div class="ph3"> -<div class='nf-center-c0'> -<div class='nf-center c003'> - <div><a id='end'></a>MODERN SCIENCE SERIES.</div> - </div> -</div> - -</div> - -<div class='nf-center-c0'> -<div class='nf-center c001'> - <div><i>Edited by Sir JOHN LUBBOCK, Bart., M. 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Books like this, -which are free from all the technicalities of science, but yet lack little that has scientific -value, are well suited to the reading of the young. Their atmosphere is a healthy -one for boys in particular to breathe.”—<cite>Boston Transcript.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>DAYS OUT OF DOORS.</cite> By <span class='sc'>Charles C. Abbott</span>. -12mo. Cloth, $1.50.</p> - -<p class='c007'>“‘Days out of Doors’ is a series of sketches of animal life by Charles C. Abbott, -a naturalist whose graceful writings have entertained and instructed the public before -now. The essays and narratives in this book are grouped in twelve chapters, named -after the months of the year. Under ‘January’ the author talks of squirrels, muskrats, -water-snakes, and the predatory animals that withstand the rigor of winter; -under ‘February’ of frogs and herons, crows and blackbirds; under ‘March’ of gulls -and fishes and foxy sparrows; and so on appropriately, instructively, and divertingly -through the whole twelve.”—<cite>New York Sun.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>THE PLAYTIME NATURALIST.</cite> By Dr. <span class='sc'>J. E. -Taylor</span>, F.L.S., editor of “Science Gossip.” With 366 Illustrations. -12mo. Cloth, $1.50.</p> - -<p class='c007'>“The work contains abundant evidence of the author’s knowledge and enthusiasm, -and any boy who may read it carefully is sure to find something to attract him. The -style is clear and lively, and there are many good illustrations.”—<cite>Nature.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>THE ORIGIN OF FLORAL STRUCTURES -through Insects and other Agencies.</cite> By the Rev. <span class='sc'>George -Henslow</span>, Professor of Botany, Queen’s College. With numerous -Illustrations. 12mo. Cloth, $1.75.</p> - -<p class='c007'>“Much has been written on the structure of flowers, and it might seem almost -superfluous to attempt to say anything more on the subject, but it is only within the -last few years that a new literature has sprung up, in which the authors have described -their observations and given their interpretations of the uses of floral mechanisms, more -especially in connection with the processes of fertilization.”—<i>From Introduction.</i></p> - -<p class='drop-capa0_0_6 c021'><cite>THE GARDEN’S STORY; or, Pleasures and -Trials of an Amateur Gardener.</cite> By <span class='sc'>George H. Ellwanger</span>. -With Head and Tail Pieces by Rhead. 12mo. Cloth, extra, -$1.50.</p> - -<p class='c007'>“Mr. Ellwanger’s instinct rarely errs in matters of taste. He writes out of the -fullness of experimental knowledge, but his knowledge differs from that of many a -trained cultivator in that his skill in garden practice is guided by a refined æsthetic -sensibility, and his appreciation of what is beautiful in nature is healthy, hearty, and -catholic. His record of the garden year, as we have said, begins with the earliest -violet, and it follows the season through until the witch-hazel is blossoming on the -border of the wintry woods.... This little book can not fail to give pleasure to all -who take a genuine interest in rural life.”—<cite>New York Tribune.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>THE ORIGIN OF CULTIVATED PLANTS.</cite> -By <span class='sc'>Alphonse de Candolle</span>. 12mo. Cloth, $2.00.</p> - -<p class='c007'>“Though a fact familiar to botanists, it is not generally known how great is the -uncertainty as to the origin of many of the most important cultivated plants.... In -endeavoring to unravel the matter, a knowledge of botany, of geography, of geology, -of history, and of philosophy is required. By a combination of testimony derived from -these sources M. de Candolle has been enabled to determine the botanical origin and -geographical source of the large proportion of species he deals with.”—<cite>The Athenæum.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>THE FOLK-LORE OF PLANTS.</cite> By <span class='sc'>T. F. Thiselton -Dyer</span>, M.A. 12mo. Cloth, $1.50.</p> - -<p class='c007'>“A handsome and deeply interesting volume.... In all respects the book is excellent. -Its arrangement is simple and intelligible, its style bright and alluring.... -To all who seek an introduction to one of the most attractive branches of folk-lore, -this delightful volume may be warmly commended.”—<cite>Notes and Queries.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>FLOWERS AND THEIR PEDIGREES.</cite> By -<span class='sc'>Grant Allen</span>, author of “Vignettes of Nature,” etc. Illustrated. -12mo. Cloth, $1.50.</p> - -<p class='c007'>“No writer treats scientific subjects with so much ease and charm of style as Mr. -Grant Allen. The study is a delightful one, and the book is fascinating to any one -who has either love for flowers or curiosity about them.”—<cite>Hartford Courant.</cite></p> - -<p class='c007'>“Any one with even a smattering of botanical knowledge, and with either a heart -or mind, must be charmed with this collection of essays.”—<cite>Chicago Evening Journal.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>THE GEOLOGICAL HISTORY OF PLANTS.</cite> -By Sir <span class='sc'>J. William Dawson</span>, F.R.S. Illustrated. 12mo. -Cloth, $1.75.</p> - -<p class='c007'>“The object of this work is to give, in a connected form, a summary of the development -of the vegetable kingdom in geological time. To the geologist and botanist the -subject is one of importance with reference to their special pursuits, and one on which -it has not been easy to find any convenient manual of information. It is hoped that its -treatment in the present volume will also be found sufficiently simple and popular to be -attractive to the general reader.”—<i>From the Preface.</i></p> - -<p class='drop-capa0_0_6 c021'><cite>THE ICE AGE IN NORTH AMERICA, and its -Bearings upon the Antiquity of Man.</cite> By <span class='sc'>G. Frederick -Wright</span>, D. D., LL. D. With 152 Maps and Illustrations. -Third edition, containing Appendix on the “Probable Cause of -Glaciation,” by <span class='sc'>Warren Upham</span>, F.G.S.A., and Supplementary -Notes. 8vo. 625 pages, and complete Index. Cloth, $5.00.</p> - -<p class='c007'>“Prof. Wright’s work is great enough to be called monumental. There is not -a page that is not instructive and suggestive. It is sure to make a reputation abroad -as well as at home for its distinguished author, as one of the most active and intelligent -of the living students of natural science and the special department of glacial action.”—<cite>Philadelphia -Bulletin.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>THE GREAT ICE AGE, and its Relation to the -Antiquity of Man.</cite> By <span class='sc'>James Geikie</span>, F.R.S.E., of H. M. -Geological Survey of Scotland. With Maps and Illustrations. -12mo. Cloth, $2.50.</p> - -<p class='c007'>A systematic account of the Glacial epoch in England and Scotland, with special -reference to its changes of climate.</p> - -<p class='drop-capa0_0_6 c021'><cite>THE CAUSE OF AN ICE AGE.</cite> By Sir <span class='sc'>Robert -Ball</span>, LL. D., F.R.S., Royal Astronomer of Ireland, author of -“Starland.” The first volume in the <span class='sc'>Modern Science Series</span>, -edited by Sir <span class='sc'>John Lubbock</span>. 12mo. Cloth, $1.00.</p> - -<p class='c007'>“An exceedingly bright and interesting discussion of some of the marvelous physical -revolutions of which our earth has been the scene. Of the various ages traced and -located by scientists, none is more interesting or can be more so than the Ice age, and -never have its phenomena been more clearly and graphically described, or its causes -more definitely located, than in this thrillingly interesting volume.”—<cite>Boston Traveller.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>TOWN GEOLOGY.</cite> By the Rev. <span class='sc'>Charles Kingsley</span>, -F.L.S., F.G.S., Canon of Chester. 12mo. Cloth, $1.50.</p> - -<p class='c007'>“I have tried rather to teach the method of geology than its facts; to furnish the -student with a key to all geology; rough indeed and rudimentary, but sure and sound -enough, I trust, to help him to unlock most geological problems which may meet him -in any quarter of the globe.”—<i>From the Preface.</i></p> - -<p class='drop-capa0_0_6 c021'><cite>AN AMERICAN GEOLOGICAL RAILWAY -GUIDE.</cite> Giving the Geological Formation along the Railroads, -with Altitude above Tide-water, Notes on Interesting -Places on the Routes, and a Description of each of the Formations. -By <span class='sc'>James Macfarlane</span>, Ph. D., and more than Seventy-five -Geologists. Second edition, 426 pp., 8vo. Cloth, $2.50.</p> - -<p class='c007'>“The idea is an original one.... Mr. Macfarlane has produced a very convenient -and serviceable hand-book, available alike to the practical geologist, to the student of -that science, and to the intelligent traveler who would like to know the country through -which he is passing.”—<cite>Boston Evening Transcript.</cite></p> - -<div class='section ph2'> - -<div class='nf-center-c0'> -<div class='nf-center c003'> - <div>WORKS BY ARABELLA B. BUCKLEY (MRS. FISHER).</div> - </div> -</div> - -</div> - -<p class='drop-capa0_0_6 c020'><cite>THE FAIRY-LAND OF SCIENCE.</cite> With 74 Illustrations. -Cloth, gilt, $1.50.</p> - -<p class='c007'>“Deserves to take a permanent place in the literature of youth.”—<cite>London Times.</cite></p> - -<p class='c007'>“So interesting that, having once opened the book, we do not know how to leave -off reading.”—<cite>Saturday Review.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>THROUGH MAGIC GLASSES and other Lectures.</cite> -A Sequel to “The Fairy-Land of Science.” Cloth, $1.50.</p> - -<div class='nf-center-c0'> - <div class='nf-center'> - <div><i>CONTENTS.</i></div> - </div> -</div> - -<div class='lg-container-b'> - <div class='linegroup'> - <div class='group'> - <div class='line'><span class='sc'>The Magician’s Chamber by Moonlight.</span></div> - <div class='line'><span class='sc'>Magic Glasses and How to Use Them.</span></div> - <div class='line'><span class='sc'>Fairy Rings and How They are Made.</span></div> - <div class='line'><span class='sc'>The Life-history of Lichens and Mosses.</span></div> - <div class='line'><span class='sc'>The History of a Lava-Stream.</span></div> - <div class='line'><span class='sc'>An Hour with the Sun.</span></div> - <div class='line'><span class='sc'>An Evening with the Stars.</span></div> - <div class='line'><span class='sc'>Little Beings from a Miniature Ocean.</span></div> - <div class='line'><span class='sc'>The Dartmoor Ponies.</span></div> - <div class='line'><span class='sc'>The Magician’s Dream of Ancient Days.</span></div> - </div> - </div> -</div> - -<p class='drop-capa0_0_6 c021'><cite>LIFE AND HER CHILDREN: Glimpses of Animal -Life from the Amœba to the Insects.</cite> With over 100 Illustrations. -Cloth, gilt, $1.50.</p> - -<p class='c007'>“The work forms a charming introduction to the study of zoölogy—the science of -living things—which, we trust, will find its way into many hands.”—<cite>Nature.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>WINNERS IN LIFE’S RACE; or, The Great -Backboned Family.</cite> With numerous Illustrations. Cloth, gilt, -$1.50.</p> - -<p class='c007'>“We can conceive no better gift-book than this volume. Miss Buckley has spared -no pains to incorporate in her book the latest results of scientific research. The illustrations -in the book deserve the highest praise—they are numerous, accurate, and -striking.”—<cite>Spectator.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>A SHORT HISTORY OF NATURAL SCIENCE; -and of the Progress of Discovery from the Time of -the Greeks to the Present Time.</cite> New edition, revised and rearranged. -With 77 Illustrations. Cloth, $2.00.</p> - -<p class='c007'>“The work, though mainly intended for children and young persons, may be most -advantageously read by many persons of riper age, and may serve to implant in their -minds a fuller and clearer conception of ‘the promises, the achievements, and claims of -science.’”—<cite>Journal of Science.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>MORAL TEACHINGS OF SCIENCE.</cite> Cloth, -75 cents.</p> - -<p class='c007'>“The book is intended for readers who would not take up an elaborate philosophical -work—those who, feeling puzzled and adrift in the present chaos of opinion, -may welcome even a partial solution, from a scientific point of view, of the difficulties -which oppress their minds.”—<i>From the Preface.</i></p> - -<div class='section ph2'> - -<div class='nf-center-c0'> -<div class='nf-center c003'> - <div>Recent Volumes of the International Scientific Series.</div> - </div> -</div> - -</div> - -<p class='drop-capa0_0_6 c020'><cite>A HISTORY OF CRUSTACEA.</cite> By Rev. <span class='sc'>Thomas -R. R. Stebbing</span>, M.A., author of “The Challenger Amphipoda,” -etc. With numerous Illustrations. 12mo. Cloth, $2.00.</p> - -<p class='c007'>“Mr. Stebbing’s account of ‘Recent Malacostraca’ (soft-shelled animals) is practically -complete, and is based upon the solid foundations of science. The astonishing -development of knowledge in this branch of natural history is due to the extension of -marine research, the perfecting of the microscope, and the general diffusion of information -regarding what has been ascertained concerning the origin of species.... This -volume is fully illustrated, and contains useful references to important authorities. It -is an able and meritorious survey of recent crustacea.”—<cite>Philadelphia Ledger.</cite></p> - -<p class='c007'>“In all respects an admirable piece of work.”—<cite>The Churchman.</cite></p> - -<p class='c007'>“One of the most valuable and entertaining volumes in the series.... The author -is master of an engaging style, and offers words of cheer and counsel to the beginner -who may be dismayed by the bewildering riches of the crustacean world. Every branch -of the subject treated is presented in the most interesting and significant light.”—<cite>London -Saturday Review.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>HANDBOOK OF GREEK AND LATIN PALÆOGRAPHY.</cite> -By <span class='sc'>Edward Maunde Thompson</span>, D.C.L., -Principal Librarian of the British Museum. With numerous -Illustrations. 12mo. Cloth, $2.00.</p> - -<p class='c007'>“Mr. Thompson, as principal librarian of the British Museum, has of course had -very exceptional advantages for preparing his book.... Probably all teachers of the -classics, as well as specialists in palæography, will find something of value in this systematic -treatise upon a rather unusual and difficult study.”—<cite>Review of Reviews.</cite></p> - -<p class='c007'>“A well-arranged manual from the hands of a competent authority.... Of the -nineteen chapters contained in the volume, seven deal with preliminary topics, as the -history of the Greek and the Latin alphabets, writing materials, the forms of books, -punctuation, measurement of lines, shorthand, abbreviations, and contractions; five -are devoted to Greek palæography, seven to Latin.”—<cite>The Critic.</cite></p> - -<p class='c007'>“Covering as this volume does such a vast period of time, from the beginning of the -alphabet and the ways of writing down to the seventeenth century, the wonder is how, -within three hundred and thirty-three pages, so much that is of practical usefulness has -been brought together.”—<cite>New York Times.</cite></p> - -<p class='drop-capa0_0_6 c021'><cite>MAN AND THE GLACIAL PERIOD.</cite> By <span class='sc'>G. -Frederick Wright</span>, D.D., LL.D., author of “The Ice Age in -North America,” “Logic of Christian Evidences,” etc. With -numerous Illustrations. 12mo. Cloth, $1.75.</p> - -<p class='c007'>“The author is himself an independent student and thinker whose competence and -authority are undisputed.”—<cite>New York Sun.</cite></p> - -<p class='c007'>“It may be described in a word as the best summary of scientific conclusions concerning -the question of man’s antiquity as affected by his known relations to geological -time.”—<cite>Philadelphia Press.</cite></p> - -<p class='c007'>“The earlier chapters describing glacial action, and the traces of it in North America—especially -the defining of its limits, such as the terminal moraine of the great movement -itself—are of great interest and value. The maps and diagrams are of much assistance -in enabling the reader to grasp the vast extent of the movement.”—<cite>London -Spectator.</cite></p> - -<div class='nf-center-c0'> -<div class='nf-center c001'> - <div>New York: D. APPLETON & CO., 1, 3, & 5 Bond Street.</div> - </div> -</div> - -<div class='pbb'> - <hr class='pb c002' /> -</div> -<div class='tnotes'> - -<div class='section ph2'> - -<div class='nf-center-c0'> -<div class='nf-center c003'> - <div>TRANSCRIBER’S NOTES</div> - </div> -</div> - -</div> - - <ol class='ol_1 c001'> - <li>P. <a href='#t70'>70</a>, changed “japonicus” to “M. japonicus”. - - </li> - <li>P. <a href='#t150'>150</a>, changed “fibres” to “fishes”. - -<p class='li-p-last c022'>.Moved advertising between half-title & Frontispiece to between the <a href='#end'>index</a> and the other advertising.</p> - </li> - <li>Silently corrected typographical errors and variations in spelling. - - </li> - <li>Archaic, non-standard, and uncertain spellings retained as printed. - </li> - </ol> - -</div> - -<div style='display:block; margin-top:4em'>*** END OF THE PROJECT GUTENBERG EBOOK THE FAUNA OF THE DEEP SEA ***</div> -<div style='display:block; margin:1em 0'> -Updated editions will replace the previous one—the old editions will -be renamed. -</div> - -<div style='display:block; margin:1em 0'> -Creating the works from print editions not protected by U.S. copyright -law means that no one owns a United States copyright in these works, -so the Foundation (and you!) can copy and distribute it in the United -States without permission and without paying copyright -royalties. 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