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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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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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