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diff --git a/old/54276-h/54276-h.htm b/old/54276-h/54276-h.htm deleted file mode 100644 index a113f0b..0000000 --- a/old/54276-h/54276-h.htm +++ /dev/null @@ -1,4983 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" - "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> -<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> - <head> - <meta http-equiv="Content-Type" content="text/html;charset=utf-8" /> - <meta http-equiv="Content-Style-Type" content="text/css" /> - <title> - The Project Gutenberg eBook of Physiology and Histology of the Cubomedusæ, by E. W. 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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/license - - -Title: Physiology and histology of the Cubomedusæ - including Dr. F.S. Conant's notes on the physiology - -Author: Edward William Berger - -Contributor: Franklin Story Conant - -Release Date: March 3, 2017 [EBook #54276] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK CUBOMEDUSAE *** - - - - -Produced by Donald Cummings, Bryan Ness and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive/American Libraries.) - - - - - - -</pre> - - -<p class="transnote">Transcriber’s Note: The images contained within black borders -are clickable for a larger version, if you are using a browser/device that supports -this functionality.</p> - -<p><span class="pagenum"><a name="Page_i" id="Page_i">[i]</a></span></p> - -<p class="titlepage">Memoirs from the Biological Laboratory<br /> -<span class="smaller">OF THE</span><br /> -JOHNS HOPKINS UNIVERSITY<br /> -<span class="smaller">IV, 4</span><br /> -WILLIAM K. BROOKS, EDITOR</p> - -<h1>PHYSIOLOGY AND HISTOLOGY<br /> -<span class="smaller">OF</span><br /> -THE CUBOMEDUSÆ</h1> - -<p class="titlepage">INCLUDING<br /> -<span class="smcap">Dr. F. S. Conant’s Notes on the Physiology</span></p> - -<p class="titlepage">A DISSERTATION PRESENTED TO THE BOARD OF UNIVERSITY STUDIES OF THE JOHNS<br /> -HOPKINS UNIVERSITY FOR THE DEGREE OF DOCTOR OF PHILOSOPHY</p> - -<p class="titlepage">BY<br /> -E. W. BERGER</p> - -<p class="titlepage">BALTIMORE<br /> -<span class="smcap">The Johns Hopkins Press</span><br /> -1900</p> - -<p><span class="pagenum"><a name="Page_ii" id="Page_ii">[ii]</a></span></p> - -<div class="figcenter titlepage" style="width: 150px;"> -<img src="images/logo.jpg" width="150" height="150" alt="Logo of the Lord Baltimore Press" /> -</div> - -<p class="titlepage smaller">PRINTED BY<br /> -<span class="larger">The Lord Baltimore Press</span><br /> -THE FRIEDENWALD COMPANY<br /> -BALTIMORE, MD., U.S.A.</p> - -<hr /> - -<p><span class="pagenum"><a name="Page_iii" id="Page_iii">[iii]</a></span></p> - -<p>This Memoir is a continuation of the work upon the Cubomedusæ -which was begun by the late Dr. <span class="smcap">Franklin Story Conant</span>, and it -contains his notes of physiological experiments, as well as new results -which have been obtained by Dr. <span class="smcap">E. W. Berger</span> from the study of -material which had been collected by Dr. <span class="smcap">Conant</span>, who had hoped to -make it the object of further study.</p> - -<p>In order that this work may be made public as a continuation of -Dr. <span class="smcap">Conant’s</span> researches, his sister, <span class="smcap">Grace Wilbur Conant</span>, has, with the -coöperation of other members of his family, made an adequate and -generous provision for its publication.</p> - -<p>For this gift, which is at once a contribution to science and a -memorial of an able and promising investigator, lately student and -fellow in this institution, the Johns Hopkins University returns its -grateful acknowledgments.</p> - -<p class="right">DANIEL C. GILMAN, <i>President</i>.<br /> -W. K. BROOKS, <i>Professor of Zoölogy</i>.</p> - -<p><span class="pagenum"><a name="Page_iv" id="Page_iv">[iv]</a></span></p> - -<hr /> - -<p><span class="pagenum"><a name="Page_v" id="Page_v">[v]</a></span></p> - -<h2>CONTENTS.</h2> - -<table summary="Contents"> - <tr> - <td></td> - <td class="right smaller">PAGE</td> - </tr> - <tr> - <td><a href="#INTRODUCTION">INTRODUCTION.</a></td> - <td></td> - </tr> - <tr> - <td class="level2">History</td> - <td class="right"><a href="#Page_1">1</a></td> - </tr> - <tr> - <td class="level2">Epitome of Anatomy</td> - <td class="right"><a href="#Page_2">2</a></td> - </tr> - <tr> - <td><a href="#PHYSIOLOGICAL">PHYSIOLOGICAL.</a></td> - <td></td> - </tr> - <tr> - <td class="level2"><span class="smcap">Charybdea.</span></td> - <td></td> - </tr> - <tr> - <td class="level3">Light and Darkness</td> - <td class="right"><a href="#Page_5">5</a></td> - </tr> - <tr> - <td class="level3">Concretions</td> - <td class="right"><a href="#Page_8">8</a></td> - </tr> - <tr> - <td class="level3">Sensory Clubs</td> - <td class="right"><a href="#Page_9">9</a></td> - </tr> - <tr> - <td class="level3">Velarium and Frenula</td> - <td class="right"><a href="#Page_11">11</a></td> - </tr> - <tr> - <td class="level3">Pedalia, Interradial Ganglia, Tentacles</td> - <td class="right"><a href="#Page_12">12</a></td> - </tr> - <tr> - <td class="level3">Stomach, Suspensoria, Proboscis, Subumbrella</td> - <td class="right"><a href="#Page_13">13</a></td> - </tr> - <tr> - <td class="level3">Margin, Radial Ganglia, Nerve</td> - <td class="right"><a href="#Page_15">15</a></td> - </tr> - <tr> - <td class="level3">Stimulation</td> - <td class="right"><a href="#Page_17">17</a></td> - </tr> - <tr> - <td class="level3">Activity of Charybdea</td> - <td class="right"><a href="#Page_17">17</a></td> - </tr> - <tr> - <td class="level3">Temperature</td> - <td class="right"><a href="#Page_17">17</a></td> - </tr> - <tr> - <td class="level3">Food and Feeding</td> - <td class="right"><a href="#Page_18">18</a></td> - </tr> - <tr> - <td class="level3">Occurrence of Charybdea</td> - <td class="right"><a href="#Page_18">18</a></td> - </tr> - <tr> - <td class="level2"><span class="smcap">Aurelia and Polyclonia</span> (<i>Cassiopœa</i>)</td> - <td class="right"><a href="#Page_19">19</a></td> - </tr> - <tr> - <td class="level2"><span class="smcap">Summary</span></td> - <td class="right"><a href="#Page_22">22</a></td> - </tr> - <tr> - <td><a href="#DR_CONANTS_NOTES">DR. CONANT’S NOTES.</a></td> - <td></td> - </tr> - <tr> - <td class="level2"><span class="smcap">Charybdea.</span></td> - <td></td> - </tr> - <tr> - <td class="level3">Light and Darkness</td> - <td class="right"><a href="#Page_24">24</a></td> - </tr> - <tr> - <td class="level3">Sensory Clubs</td> - <td class="right"><a href="#Page_26">26</a></td> - </tr> - <tr> - <td class="level3">Nerve</td> - <td class="right"><a href="#Page_29">29</a></td> - </tr> - <tr> - <td class="level3">Side, Subumbrella</td> - <td class="right"><a href="#Page_30">30</a></td> - </tr> - <tr> - <td class="level3">Pedalia, Velarium, Ganglia</td> - <td class="right"><a href="#Page_31">31</a></td> - </tr> - <tr> - <td class="level3">Tentacles</td> - <td class="right"><a href="#Page_32">32</a></td> - </tr> - <tr> - <td class="level3">Proboscis, Stomach, Phacelli</td> - <td class="right"><a href="#Page_33">33</a></td> - </tr> - <tr> - <td class="level3">Temperature</td> - <td class="right"><a href="#Page_33">33</a></td> - </tr> - <tr> - <td class="level3">Food and Feeding</td> - <td class="right"><a href="#Page_33">33</a></td> - </tr> - <tr> - <td class="level3">Occurrence of Charybdea</td> - <td class="right"><a href="#Page_33">33</a></td> - </tr> - <tr> - <td class="level3">Activity of Charybdea</td> - <td class="right"><a href="#Page_34">34</a></td> - </tr> - <tr> - <td class="level2"><span class="smcap">Aurelia and Polyclonia</span></td> - <td class="right"><a href="#Page_35">35</a></td> - </tr> - <tr> - <td class="level2"><span class="smcap">Cassiopœa</span></td> - <td class="right"><a href="#Page_39">39</a></td> - </tr> - <tr> - <td class="level2"><span class="pagenum"><a name="Page_vi" id="Page_vi">[vi]</a></span><span class="smcap">Aurelia</span></td> - <td class="right"><a href="#Page_39">39</a></td> - </tr> - <tr> - <td><a href="#HISTOLOGICAL">HISTOLOGICAL.</a></td> - <td></td> - </tr> - <tr> - <td class="level2">Method</td> - <td class="right"><a href="#Page_40">40</a></td> - </tr> - <tr> - <td class="level2">Anatomy</td> - <td class="right"><a href="#Page_41">41</a></td> - </tr> - <tr> - <td class="level2">Distal Complex Eye—</td> - <td></td> - </tr> - <tr> - <td class="level3">General</td> - <td class="right"><a href="#Page_41">41</a></td> - </tr> - <tr> - <td class="level3">Cornea</td> - <td class="right"><a href="#Page_42">42</a></td> - </tr> - <tr> - <td class="level3">The Lens</td> - <td class="right"><a href="#Page_42">42</a></td> - </tr> - <tr> - <td class="level3">The Capsule</td> - <td class="right"><a href="#Page_44">44</a></td> - </tr> - <tr> - <td class="level3">The Retina</td> - <td class="right"><a href="#Page_45">45</a></td> - </tr> - <tr> - <td class="level4">(a) The Prism Cells</td> - <td class="right"><a href="#Page_46">46</a></td> - </tr> - <tr> - <td class="level4">(b) The Pyramid Cells</td> - <td class="right"><a href="#Page_48">48</a></td> - </tr> - <tr> - <td class="level4">(c) The Long Pigment Cells</td> - <td class="right"><a href="#Page_50">50</a></td> - </tr> - <tr> - <td class="level4">(d) Subretinal Nerve Tissue</td> - <td class="right"><a href="#Page_53">53</a></td> - </tr> - <tr> - <td class="level4">(e) Discussion of Literature</td> - <td class="right"><a href="#Page_53">53</a></td> - </tr> - <tr> - <td class="level4">(f) Function of the Retinal Cells, Patten’s Theory, and further Literature</td> - <td class="right"><a href="#Page_56">56</a></td> - </tr> - <tr> - <td class="level2">The Proximal Complex Eye</td> - <td class="right"><a href="#Page_60">60</a></td> - </tr> - <tr> - <td class="level2">The Simple Eyes</td> - <td class="right"><a href="#Page_61">61</a></td> - </tr> - <tr> - <td class="level2">Lithocyst and Concretion</td> - <td class="right"><a href="#Page_63">63</a></td> - </tr> - <tr> - <td class="level2">The Epithelium of the Clubs</td> - <td class="right"><a href="#Page_64">64</a></td> - </tr> - <tr> - <td class="level2">Network and Multipolar Ganglion Cells</td> - <td class="right"><a href="#Page_67">67</a></td> - </tr> - <tr> - <td class="level2">The Nerve Tissue</td> - <td class="right"><a href="#Page_67">67</a></td> - </tr> - <tr> - <td class="level2">The Supporting Lamella</td> - <td class="right"><a href="#Page_68">68</a></td> - </tr> - <tr> - <td class="level2">Epithelium of Ampulla and Floating Cells</td> - <td class="right"><a href="#Page_68">68</a></td> - </tr> - <tr> - <td class="level2">The Endothelium of the Peduncle</td> - <td class="right"><a href="#Page_73">73</a></td> - </tr> - <tr> - <td class="level2">The Tentacles and Pedalia—</td> - <td></td> - </tr> - <tr> - <td class="level3">The Ectoderm</td> - <td class="right"><a href="#Page_74">74</a></td> - </tr> - <tr> - <td class="level4">(a) Thread Cells</td> - <td class="right"><a href="#Page_74">74</a></td> - </tr> - <tr> - <td class="level4">(b) Muscle Fibers</td> - <td class="right"><a href="#Page_74">74</a></td> - </tr> - <tr> - <td class="level4">(c) Ganglion Cell</td> - <td class="right"><a href="#Page_75">75</a></td> - </tr> - <tr> - <td class="level3">The Endoderm</td> - <td class="right"><a href="#Page_75">75</a></td> - </tr> - <tr> - <td class="level2"><span class="smcap">Summary</span></td> - <td class="right"><a href="#Page_77">77</a></td> - </tr> - <tr> - <td>LITERATURE</td> - <td class="right"><a href="#LITERATURE">78</a></td> - </tr> - <tr> - <td>REFERENCE LETTERS</td> - <td class="right"><a href="#REFERENCE_LETTERS">80</a></td> - </tr> - <tr> - <td>DESCRIPTION OF FIGURES</td> - <td class="right"><a href="#DESCRIPTION_OF_FIGURES">81</a></td> - </tr> -</table> - -<hr /> - -<p><span class="pagenum"><a name="Page_1" id="Page_1">[1]</a></span></p> - -<h2 id="INTRODUCTION">INTRODUCTION.</h2> - -<p>This paper may be regarded as a continuation of the Cubomedusan -studies pursued by Dr. F. S. Conant while in Jamaica, in 1896 and 1897, -with the Johns Hopkins Marine Laboratory. His systematic and -anatomical results have since been published as his Dissertation (“The -Cubomedusæ”) by this University. Conant described this paper as -Part I, hoping soon to add a second part on the physiology and the -embryology, for which he had some notes and material at hand. -Returning, however, to Jamaica with the laboratory, in 1897, he -continued his physiological experiments, and preserved material for -histological purposes. Upon the untimely death of Conant, his material -and notes were placed in my hands by Professor Brooks, to whom I -here take the opportunity of expressing my appreciation and sincere -thanks for the honor thus conferred and for the many favors received.</p> - -<p>In this paper I shall note at some length Conant’s physiological -results and append his notes. I shall also add my results on the -histology of the eyes and the sensory clubs in general, with some few -facts on the histology of the tentacles. The embryology will be -reserved for a future paper.</p> - -<p>The forms used in the physiological experiments were Charybdea -Xaymacana, one of the two species (see Literature <a href="#bookV">V, a and b</a>) -first found and described by Conant; Aurelia aurita; Polyclonia and -Cassiopœa. The greater number of Conant’s notes are on Charybdea, -and were left by him just as taken at the time of experimenting. -Many of these notes are highly interesting and in the main fit in -well with Romanes’<span class="fnanchor"><a href="#bookI">[I]</a></span> and Eimer’s<span class="fnanchor"><a href="#bookIV">[IV]</a></span> results.</p> - -<p>Dr. Conant’s work on Charybdea, in 1897, was wholly done at -Port Antonio, Jamaica. At first Conant had only varying success in -obtaining Charybdea, scouring the harbor and neighboring water at -all hours, only to obtain but few specimens. It was on the forenoon -of August 7th, while we were dredging at the head of East Harbor -with a steam launch, that many Charybdeæ were brought up in the -dredge. This gave Conant a clue to their whereabouts and to the -means of obtaining them, and from that time on he was able to<span class="pagenum"><a name="Page_2" id="Page_2">[2]</a></span> -obtain them in abundance. His first physiological experiments were -begun on August 4th and continued thereafter at intervals of several -days until his departure from Jamaica on September 6th.</p> - -<p>Dr. Conant usually performed his experiments during the second -half of the forenoon, after the animals had stood for a few hours in -the laboratory.</p> - -<p>The building that was rented at Port Antonio for a laboratory -had, in the basement, a photographer’s dark-room, which was of great -service to Conant in his experiments.</p> - -<p>The experiments on Aurelia, in 1897, were also performed at -Port Antonio, between August 6th and 9th. The experiments on -Cassiopœa were probably made at Port Antonio, where specimens -were occasionally obtained.</p> - -<p>The notes on Aurelia and Polyclonia, in 1896, were taken at Port -Henderson, between May 12th and June 27th.</p> - -<p>In his notes Conant speaks of Polyclonia and Cassiopœa. It is -at present undetermined whether he really had both forms or whether -he uses the two names for the same form. It seems likely that in -1896 he thought the form to be Polyclonia, while for some reason, -in 1897, he supposed it to be Cassiopœa. I have examined several -specimens of these medusæ brought from Port Antonio and find that -they all have twelve marginal bodies and twenty-four radial canals, -according to which (<a href="#bookV">V, Haeckel’s System</a>), they should be Polyclonia. -Conant, however, speaks of removing sixteen marginal bodies, which -seems to indicate that he had Cassiopœa. A careful classification -of this form of medusæ found about Jamaica seems to be a desideratum. -I suppose, however, that for our purpose in this paper it will make -little difference which name is used, the two forms being so similar -in form and structure. I have, therefore, decided to retain both the -names used by Conant.</p> - -<p>For the complete anatomy of Charybdea the reader is referred -to Dr. Conant’s dissertation, “The Cubomedusæ” (<a href="#book8b">8b</a>), or the <cite>Johns -Hopkins University Circulars</cite> (<a href="#book8a">8a</a>), both published by the Johns -Hopkins Press. But, for the convenience of those who may be less -familiar with Cubomedusan anatomy, the following brief summary -of the anatomy of Charybdea is given:</p> - -<p>The Cubomedusæ, as the name implies, approximate cubes, with -their tentacles (four in Charybdea) arranged at the four corners of -the lower face of the cube. These tentacles are said to lie in the<span class="pagenum"><a name="Page_3" id="Page_3">[3]</a></span> -interradii. Half way between any two points of attachment of the -pedalia (the basal portions of the tentacles) and a little above the -margin of the bell (cube), in a niche, hang the sensory clubs, one on -each side, four in all. Each sensory club hangs in a niche of the -exumbrella and is attached by a small peduncle whose axial canal -is in connection with one of the four stomach-pockets and in the -club proper forms an ampulla-like enlargement.</p> - -<p>Each club is said to lie in a perradius, and, like the tentacles, -belongs to the subumbrella. This is shown by the course of the -vascular lamellæ, bands of cells that, stretching through the jelly -from the endoderm to the ectoderm all around the margin, form the -line of division between sub- and exumbrella.</p> - -<p>Each club has six eyes. Two of these on the middle line of the -club facing inwards are called the proximal and distal complex eyes, -to distinguish them from the four simple eyes that are disposed -laterally, two on each side of the line of the two complex eyes. All of -these eyes look inwards into the bell cavity through a thin transparent -membrane of the subumbrella. Besides the eyes and the ampulla -already mentioned, a concretion fills the lowermost part of the club, -and a group of large cells, having a network-like structure and called -network cells by Conant, fill the uppermost part of the club between -the proximal complex eye and the attachment of the club to its -peduncle (<a href="#plate2">Plate II, Fig. 13</a>). What is evidently nerve tissue, fibers and -ganglion cells, fills the rest of the club, with two groups of large -ganglion cells disposed laterally from the network cells. A sensory -(flagellate) epithelium covers the club.</p> - -<p>Most Cubomedusæ, among them Charybdea, have a velarium -(comparable to the velum of the Hydromedusæ), a membrane of -tissue that extends inwards at right angles all around the margin. -This velarium, like a velum, has a central opening through which -the water is expelled from the bell-cavity when the animal pulsates. -In the perradii and in the angle between the velarium and the body -wall, are the frenula, which give support to the velarium much like -brackets support a shelf, except that here the brackets are above the -shelf instead of below.</p> - -<p>In the upper part of the bell is the stomach, with the phacelli in -its interradii, and continued ventrally into the manubrium, or the -proboscis. The cavity of the stomach is continued in the perradii -through the four gastric ostia into the four stomach pockets, which<span class="pagenum"><a name="Page_4" id="Page_4">[4]</a></span> -occupy the sides of the bell and extend to the margin. Immediately -below the gastric ostia, and in the bell cavity, are the suspensoria, one -in each perradius. These support the floor of the stomach much as the -frenula support the velarium, except that the suspensoria are placed -under the shelf (to continue Conant’s figure) and not above it as are -the frenula.</p> - -<p>A nerve ring, underneath the epithelium of the subumbrella, -passes from near the origin of each pedalium at the margin to the -origin of the peduncles of the sensory clubs, a little above the margin, -giving off a branch to each club. Eight ganglia are found in the -course of this nerve. The four pedal ganglia lie near the bases of -the pedalia, and are hence interradial; the four radial ganglia lie -near the bases of the peduncles of the clubs, and are perradial. A -small nerve, radial nerve, can be traced a short distance upwards -from each radial ganglion. Underlying the epithelium of the frenula -and the suspensoria are ganglion cells and nerve fibers in larger -numbers than elsewhere (excepting the ganglia mentioned) in the -subumbrella. Otherwise, ganglion cells and nerve fibers underlie the -epithelium of the subumbrella, including the inner surface of the -velarium, as also do muscle fibers, except in the perradii and in the -region of the nerve, where the latter become interrupted.</p> - -<hr /> - -<p><span class="pagenum"><a name="Page_5" id="Page_5">[5]</a></span></p> - -<h2 id="PHYSIOLOGICAL">PHYSIOLOGICAL.</h2> - -<h3><span class="smcap">Charybdea.</span></h3> - -<p class="section"><i>Light and Darkness</i>—Experiments <a href="#exp1">1-9</a>, <a href="#exp10">10</a>, <a href="#exp33">33</a>, <a href="#exp34">34</a>.—As already stated -in the Introduction, a part of Conant’s experiments were performed -in a photographer’s dark-room, with the animals in a deep glass jar. -In the dark a fair proportion of the animals became nearly quiescent -on the bottom, but upon lighting a lamp many started up immediately, -while others took a longer time to come to the surface and swim. -These experiments were tried a number of times and on different -occasions with very similar results. Some medusæ, however, tried -immediately after being brought in, seemed not to react so well upon -being placed in the dark-room, nor would they become quiescent. -This, probably, was due to the fact that the animals had not yet -recovered from the effects of being caught and placed in new -surroundings. (Experiments <a href="#exp1">1</a>, <a href="#exp2">2</a>, <a href="#exp3">3</a>.)</p> - -<p>Other experiments (<a href="#exp4">4-8</a>, <a href="#exp33">33</a>, <a href="#exp34">34</a>) were tried by carrying the jar -with the animals from the weaker light of a room into the more -intense light of outdoors or into direct sunlight. The usual result -was an inhibition of pulsation and a settling to the bottom, while -the medusæ immediately became active again upon returning with -them to the room. These results were so marked that no doubts can -be entertained as to their cause, though some exceptions occurred in -which animals placed in the sun continued to swim on the surface -or soon recovered pulsation. In some experiments, too, no animals -responded to the inhibitory stimulus of the brighter light or all very -soon recovered. (See, however, Temperature.)</p> - -<p>Reducing the light by placing a coat over the jar produced -the same effect in some experiments (<a href="#exp8">8</a>, <a href="#exp9">9</a>, <a href="#exp10">10</a>) as did reducing the -light in other ways, while removing the coat produced the same -effect as exposure to brighter light. In these instances it appears -to be the transition from weaker to stronger light that inhibits -pulsation, rather than the actual intensity of the light; and <i>vice versa</i>. -It must be noted, too, that when left for some time in any one place<span class="pagenum"><a name="Page_6" id="Page_6">[6]</a></span> -the animals changed, some coming to the surface and others going -to the bottom.</p> - -<p>These experiments show beyond doubt that Charybdea is sensitive -to light, and that it is moderate light that stimulates the animals to -activity, while darkness and strong light inhibit activity. While the -individual exceptions, as Conant himself suggests, are well explained -on the supposition of individual diversity, yet it appears that other -conditions, such as the time of day, temperature, etc., may have been -responsible for some of the exceptional experiments in which no -animals responded as expected.</p> - -<p>While light of any intensity seems to have stimulated Romanes’<span class="fnanchor"><a href="#bookI">[I]</a></span> -Sarsia and Tiaropsis (Hydromedusæ) to activity, we note that it -is moderate light that stimulates Charybdea. This fact is evidently -correlated with the circumstance that Charybdea usually lives upon -or near the bottom.</p> - -<p>It may further be added in regard to Romanes’ Tiaropsis -polydiademata, that when it was suddenly exposed to light it went -into a spasm preceded by a long latent period during which there -was a “summation of stimulating influence” in the ganglia. Sarsiæ -would congregate toward the source of light and in general were -more active in light than in the dark, while sudden darkness often -inhibited a swimming bout. Romanes proves for Sarsia that -the marginal bodies are the seat of luminous stimulation and -that it is the light rays and not heat rays that stimulate. He -also remarks that he has obtained similar results on the covered-eyed -(Scyphomedusæ) medusæ, namely, that they respond to luminous -stimulation.</p> - -<p>It may here be of interest to note a few observations made by -myself at Wood’s Holl, Mass., on a beautiful Olindiad, which is -abundant in the Eelpond at the above place. I found that in a -room, in the ordinary light of evening, the animals swam actively; -but the moment the electric light was turned on they stopped swimming -and settled to the bottom or attached themselves to a branch -of some weed or stem suspended in the water. This was the result -in every trial. It is found, further, to be little active during the -brighter parts of the day, when one must dip quite deep with a net -in order to obtain it. A similar observation is also made by -Murbach<span class="fnanchor"><a href="#bookII">[II]</a></span>, who further states that this medusa may be deceived -into laying its eggs by placing it in the dark.</p> - -<p><span class="pagenum"><a name="Page_7" id="Page_7">[7]</a></span></p> - -<p>One cannot help but remark how analogous is the behavior of -medusæ, in respect to light and darkness, to the behavior of many -of the higher animals,—and medusæ are among the most lowly -organized of the animal creation.</p> - -<p>Were one to conclude from the behavior of Charybdea in light -and darkness in the laboratory, that it remained on or near the -bottom in the daytime but became more active near or at the -surface evenings, nights and early mornings, one would probably not -be far from the truth. Dr. Conant, while towing near the bottom -with a weighted net, in water four to five feet (1.2-1.5 m.) deep not far -from shore and deeper farther out, found Charybdea in abundance -mornings and afternoons, but very few in the evening. In the -evening some few were usually taken in the surface tow. (See Introduction, -Occurrence and Activity.)</p> - -<p>Again, who knows but that Charybdea is active during the day, -on the bottom where it was dredged (the light there would only be -moderate), and quiet at night. This supposition would seem to be -true, at least, for those forms of Cubomedusæ that live in deep -water. We can hardly suppose that they should regularly rise to -the surface from great depths and become active. This much we do -know that bright light inhibits Charybdea’s activities, while it -probably would not be active in perfect darkness.</p> - -<p>I do not know just what interpretation to put upon Conant’s -finding Charybdea at Port Henderson at the surface during the -early part of the forenoon, before the sea-breeze roughened the water -(“Cubomedusæ” p. 7). This fact hardly fits in with my conclusions -above. Perhaps Charybdea’s habits vary with its habitat.</p> - -<p>Finally, while I find no experimental evidence in Conant’s notes -about what parts of Charybdea are sensitive to light, yet it would -seem preposterous, from histological evidence and from Romanes’ -results on Sarsia, to doubt that the eyes of the marginal bodies are -the seat of this stimulation.</p> - -<p>Dr. Conant further experimented by cutting off certain organs -and parts from the Cubomedusan bell. These excisions consisted -chiefly in cutting out the concretions of the sensory clubs, cutting off -the whole club, eliminating a part or whole of the margin and the -velarium, cutting the bell into sectors, excising the stomach and -parts connected with it, and other parts.</p> - -<p><span class="pagenum"><a name="Page_8" id="Page_8">[8]</a></span></p> - -<p class="section"><i>Concretions</i>—Experiments <a href="#exp10">10</a>, <a href="#exp11">11</a>.—The four concretions were -removed from each of four animals. Two of these (Experiments <a href="#exp10">10</a>, -and another (X), not appended, to save space) seemed to be little if -at all affected by the operation. One of the two (<a href="#exp10">10</a>) swam actively, -at first up and down more changeably than those intact, but later -mostly near the surface. The other one also swam actively and -showed nothing to indicate weakened sense-perception. The other -two (<a href="#exp11">11</a>) did not stand the operation well, as Conant remarks, and -immediately went to the bottom, where they remained, one swimming, -while eight hours later one was still in good condition.</p> - -<p>Several attempts with stronger light by removing the coat from -the jar made no difference in the behavior of <a href="#exp10">10</a>; it continued to -swim as heretofore. Upon a final trial, however, with removing the -coat, it went to the bottom, thus showing a possible reaction to light; -but when next seen it was keeping to the bottom.</p> - -<p>That the concretions should function as organs of light sensation, -as the first of the above animals might seem to indicate, I believe is -out of the question.<a name="FNanchor_1" id="FNanchor_1"></a><a href="#Footnote_1" class="fnanchor">[a]</a> The fact, too, that this same animal (<a href="#exp10">10</a>), together -with another (X), swam actively, immediately changing their course -upon coming to the surface, in reality behaving quite as normal -animals, hardly permits us to conclude from the behavior of the -other two (<a href="#exp11">11</a>) that the concretions function directly as organs of -equilibrium or space relations. May these concretions not function -simply as weights for keeping the sensory clubs with their eyes -properly suspended? Since these concretions lie at the lowermost part -of the clubs and in closed sacs and unsupported by cilia, it would -seem that the above suggestion as to their being weights is not -improbable. Direct observation (Experiment <a href="#exp20">20</a>) by Conant shows, -furthermore, that the clubs always hang with a tendency for the -concretions to be lowermost, regardless of the position of the animal.</p> - -<p>Again, while they may function as weights, as just explained, -the fact that the epithelium of the clubs is flagellated (a flagellum, -continued as a nerve fiber, to each cell—see Histology), the supposition -lies near that these flagella are the ones influenced by the concretions -as the clubs bear against one side of the sensory niche or the other.<span class="pagenum"><a name="Page_9" id="Page_9">[9]</a></span> -A somewhat similar view seems to be held by other observers and -is noted by Lang in his text-book (“The outer epithelium of the -auditory body carries the auditory hairs”). It seems, then, that in -functioning as weights for suspending the clubs, they may also serve -at the same time for making the pressure of the club against the -niche greater than if they were absent, and thus in part serve in -equilibrium. On this supposition we should expect, furthermore, that -after the removal of the concretions the animal would be little, -if at all, affected, since the clubs themselves, without the concretions, -would still be of sufficient weight to be influenced by gravity and thus -to bear against the walls of the sensory niche. It must be noted, -however, that Conant’s experiments upon equilibration in Charybdea are -negative. Also, that Charybdea has any auditory sense is negatived by -two attempts of Conant’s with a violin—one attempt with the violin -near the animals, and another with it in contact with the dish. (From -an unpublished note.) Hence, some other word such as sensory or -equilibrating should perhaps be substituted for “auditory” in the -above quotation.</p> - -<p>Removing the concretions from Aurelia gave negative results very -similar to those on Charybdea. (Experiment <a href="#exp42">42</a>.)</p> - -<p class="section"><i>Sensory Clubs</i>—Experiments <a href="#exp12">12-19</a>, <a href="#exp20">20</a>, <a href="#exp24">24</a>.—The entire sensory clubs -were removed from a number of animals. A paralysis of pulsation -followed by a rapid recovery was the usual result. In some instances, -however, there was no paralysis, while in others no recovery followed -paralysis. This is true in a general way whether one club only or all -were removed. While no permanent paralysis followed the removal -of one or two clubs, yet permanent paralysis did occur after the -removal of a third club, as, of course, also after the removal of a -fourth. It is evident, too, that as the removal of the clubs progressed -recovery seemed to be weaker after each cutting, except in one case -when pulsation seemed to be quickened after the removal of a second -club. The pulsations after recovery seemed to be not so strong and -regular, often quite feeble, and in one instance in groups. Pieces of -tissue with a club attached and pulsating regularly, ceased pulsating -after removal of the club, in one instance, however, still giving -occasional contractions.</p> - -<p>These results are quite the same as those of Romanes<span class="fnanchor"><a href="#bookI">[I]</a></span> on -Aurelia, Cyanæa, etc., and of Eimer<span class="fnanchor"><a href="#bookIV">[IV]</a></span> on Aurelia, Rhizostoma,<span class="pagenum"><a name="Page_10" id="Page_10">[10]</a></span> -Cotylorhyza, etc.<a name="FNanchor_2" id="FNanchor_2"></a><a href="#Footnote_2" class="fnanchor">[b]</a> In these forms Romanes sometimes obtained -complete paralysis after the removal of the sensory clubs only, as also -after the removal of the whole margin, though this was not marked -in Aurelia. In Cyanæa and other forms motor centers seemed to -be more abundant than in Aurelia, so that paralysis was oftener -followed by recovery. He concludes that while the principal motor -centers reside in the lithocysts, other centers doubtless exist that -may function vicariously, but that the centers of the margin are -more definitely limited to the marginal bodies in the Scyphomedusæ -than in the Hydromedusæ, in which the whole margin seems to be -replete with centers. He feels positive, furthermore, that no motor -centers exist in Aurelia’s margin outside of the marginal bodies -(lithocysts). Eimer’s results are essentially the same as Romanes’, -so that for a more detailed comparison of the two, Romanes’ works -should be consulted.</p> - -<p>Romanes’ conclusion for the Hydromedusæ is that the motor -centers are not so definitely localized in the marginal bodies, but -in the margin generally, the excision of the marginal bodies alone -producing only partial paralysis, as would also the removal of the -margin from between the marginal bodies, but not so marked. -For the Hydromedusæ he concludes, then, that all the centers of -spontaneity are definitely localized in the margin, but not limited -to the marginal bodies. To this he mentions one exception, namely, -<i>Staurophora laciniata</i>, in which another center is found near the -margin and two others in two opposite arms of the proboscis.</p> - -<p>I made the remark in an abstract (<a href="#bookVI">VI</a>) on Conant’s notes that -Romanes did not obtain recovery of pulsation after removal of all -the lithocysts in Aurelia. As noted above, he did obtain recovery, so -that Conant’s results on Charybdea and also Aurelia (see Polyclonia -and Aurelia) are quite in agreement with Romanes.</p> - -<p>The paralysis following the removal of the clubs in Charybdea is -evidently, primarily, the result of a loss of a part of its nervous -mechanism (motor centers), and, secondarily, of nervous shock, and -points to the existence of a definite nervous mechanism in the -clubs. The histological evidence is here, as usual, corroborative of the -physiological.</p> - -<p>Another interesting phenomenon observed after the removal of<span class="pagenum"><a name="Page_11" id="Page_11">[11]</a></span> -one or all of the clubs was the strange behavior of the proboscis. -This would reach from side to side, expanding and contracting its -lips as if trying to grasp something. This behavior is very similar to -that of the proboscis of <i>Tiaropsis indicans</i> when Romanes stimulated -any part of its subumbrella, or of <i>Limnocodium sorbii</i>, a little fresh-water -medusa, when he stimulated its margin or the region of the -radial canals. (Ib., p. 242.)</p> - -<p>I may add that I observed a very similar movement of the -proboscis of the Olindiad, before mentioned. When I pulled off pieces -of its gonads by means of quick jerks, with a small forceps, it would -continually reach toward the injured part of its subumbrella. This -medusa is generally quite active with its proboscis and can occasionally -be seen to reach with it.</p> - -<p>Romanes states in one place that the proboscis is not affected by the -excision of the margin. This is evidently not the case in Charybdea, -in which excision of the sensory clubs (which really belong to the -margin—see “Cubomedusæ”) decidedly stimulated the proboscis to -active movements. This, furthermore, points to the marginal bodies -as being organs of considerable importance in giving information in -the life of Charybdea. In Romanes’ Sarsia and other medusæ, however, -the proboscis did respond to the stimulation of the tentacles and the -marginal bodies, as also would the bell respond to a stimulation of -the proboscis (manubrium), thus showing a reflex nervous connection -between these regions of the bell, similar to that described for -Charybdea.</p> - -<p class="section"><i>Velarium and Frenula</i>—Experiments <a href="#exp18">18</a>, <a href="#exp29">29</a>, <a href="#exp30">30</a>, <a href="#exp41">41c</a>.—“The power -of originating contractions” to use Conant’s own words, “evidently -resides in the velarium or in ganglion cells of the frenula, just -as it does in the proboscis and the floor of the stomach.” Isolated -pieces of the velarium contracted by themselves as did the whole -velarium when all other tissue had been removed. An isolated velarium -with the margin and the pedalia attached gave irregular contractions. -When the pedalia with the <em>interradial ganglia</em> were removed it still -contracted; and when all the other tissue was cut off contractions -continued.</p> - -<p>Cutting the velarium caused the <em>pedalia</em> to be strongly contracted -inwards so that the tentacles were brought inside the bell. Cutting -away the velarium did not interfere with the pulsations of the bell, -but progress was much retarded.</p> - -<p><span class="pagenum"><a name="Page_12" id="Page_12">[12]</a></span></p> - -<p>Cutting the frenula caused the pedalia to contract but seemed -not to affect the ability to swim. Comparing the velarium of the -Cubomedusæ with the velum of the Hydromedusæ, I recall no -observations similar to the ones here noted, though it seems that the -two may have quite similar functions. It seems somewhat probable -that the velum, and also the velarium, may function in obtaining -food,—and this besides their function in swimming. Their probable -function in swimming, as is well known, is evidently to narrow the -mouth of the bell and thus to cause the water to be forced out in a -smaller but more rapid stream, giving the animal a steady and more -prolonged movement through the water at every contraction of the -bell. In regard to taking food, I observed that a small crustacean, in -the process of being swallowed by an Olindiad, seemed to be held by -the velum being firmly contracted about it while the proboscis was -working itself over the crustacean. It would seem, furthermore, that -my supposition is supported for Charybdea by the fact that the -pedalia and tentacles were contracted so as to be brought inside the -bell when the velarium was cut. The stimulus of cutting the velarium -may be comparable to a stimulus from some object touching it, and -thus cause the pedalia and tentacles to come reflexly to aid in -capturing or holding the object, a fish, crustacean, or such, to be -captured.</p> - -<p class="section"><i>Pedalia, Interradial Ganglia, Tentacles</i>—Experiments <a href="#exp15">15</a>, <a href="#exp23">23</a>, <a href="#exp27">27-31</a>, -<a href="#exp41">41b</a>.—When the pedalia were removed, the power of the animal to guide -itself was completely gone. When one pedalium was cut the others -contracted, while stroking the outer edge of the pedalia, touching the -sensory clubs, or sharply pricking the subumbrella, often produced the -same result. (See also Nerve.) The upper part of the subumbrella -seemed not so sensitive and more seldom produced the reflex of the -pedalia, while the base of the stomach did not give it at all. Stroking -the outer edge of the pedalia of <i>Tripedalia cystophora</i>, the second of the -two species of Cubomedusæ described by Conant, also caused the pedalia -to be contracted inwards. I may note here that the muscle fibers under -the ectoderm of the pedalia are specially well developed at and near the -inner and outer edges, both in Charybdea and Tripedalia. On the -flattened sides of the pedalia the muscle fibers are fewer.</p> - -<p>When the pedalia were cut off far enough up to remove the -interradial ganglia, coördination was not affected and the animal<span class="pagenum"><a name="Page_13" id="Page_13">[13]</a></span> -could pulsate well enough but with little progress. (See above under -Velarium and Frenula.)</p> - -<p>An isolated tentacle is capable of squirming contractions, and -when stimulated at either end, it would contract wholly or in part -only.</p> - -<p>The pedalia, then, it would seem, serve also as a steering apparatus, -for which they are admirably fitted, considering their blade-like -thinness.</p> - -<p>Considering, now, the reflexes noted under this head and the -preceding one, we find that there is an intimate nervous connection -between the velarium and frenula, subumbrella, sensory clubs, nerve, -and a single pedalium, on the one hand, and the pedalia on the other -hand. This is born out fully, furthermore, by the histological evidence—(See -Introduction and “Cubomedusæ”). Considering the subumbral -plexus of ganglion cells and fibers, including the velarium and the -frenula, which is in connection with the nerve ring and this again -with the sensory clubs and the interradial ganglia at the bases of -the pedalia, we have a basis for these reflexes. While Conant failed -to demonstrate nerves (“Cubomedusæ”) from the interradial ganglia -to the pedalia, yet, that a nervous connection exists between the -pedalia and the bell is well shown by his physiological experiments. -I have, furthermore, demonstrated ganglion cells under the ectoderm -of the tentacles (see Histology).</p> - -<p>Romanes obtained quite similar results in the Hydromedusæ. He -found that when a tentacle of Sarsia was slightly stimulated, it alone -would contract, but when it was more strongly stimulated the other -tentacles also would respond as also the manubrium. I find no evidence -in Conant’s notes of any such response of the manubrium of Charybdea, -except when the clubs were cut off.</p> - -<p>The reflex obtained on stimulating the subumbrella of Charybdea, -when the pedalia would contract, is somewhat different from that -obtained by Romanes, who found that the most sensitive part of the -subumbrella in producing a reflex of the margin was at the junction -of the manubrium to the bell and that the subumbrella below this -point did not give the reflex.</p> - -<p class="section"><i>Stomach, Suspensoria, Proboscis, Subumbrella</i>—Experiments <a href="#exp12">12</a>, <a href="#exp18">18</a>, -<a href="#exp19">19</a>, <a href="#exp24">24-26</a>, <a href="#exp29">29</a>, <a href="#exp31">31</a>.—The proboscis and the stomach with the phacelli -when cut out, contracted with or without the lips removed. The -isolated lips also contracted (twitched).</p> - -<p><span class="pagenum"><a name="Page_14" id="Page_14">[14]</a></span></p> - -<p>Pieces of the sides connected only with the stomach and suspensoria, -or with the margin (Experiment <a href="#exp47">47</a> (?)) twitched spontaneously, -but seldom did so when these were removed. In one instance the -whole side was cut out so as to exclude the radial ganglion but still -connected with a portion of the suspensorium. This pulsated, or -contracted, but on being halved transversely, the lower half ceased to -contract while the upper half connected with the suspensorium, -continued to contract.</p> - -<p>Cutting off the whole stomach end of the animal excited to very -rapid pulsations of the remaining part, with the stream of water -stronger out the aboral end than past the velarium.</p> - -<p>Conant says, “It seems I get no good evidence of the subumbrella -without connection with special nerve centers being able to contract -by itself.” The piece in which he did get contractions he suspects -may have been intimately associated with some part of the frenula -or the suspensoria. In Polyclonia no such doubt exists, for small -pieces of subumbrella were seen to contract. A small piece of -subumbrella of Charybdea with a sensory club attached could contract -by itself.</p> - -<p>From the above it would seem that a center capable of inciting -to contractions resided in the suspensoria as well as in the sensory -clubs, and this may be one of the centers that becomes potent upon -the removal of the clubs. This is further supported by Conant’s -observation (Introduction and “Cubomedusæ”) that an extra large -number of ganglion cells is found under the epithelium of the -suspensoria. A somewhat similarly located center of spontaneity -described by Romanes for <i>Staurophora laciniata</i> (Hydromedusa) has -already been noted.</p> - -<p>As to the rapid pulsations of the bell after cutting out the -stomach end, this also is similar to Romanes’ results on Aurelia and -other Scyphomedusæ, when he cut off parts of the manubrium or an -aboral ring out of the bell. In these instances, however, Romanes -soon obtained a slackening of the rhythm following the temporary -acceleration. The temporary acceleration he attributes to the stimulus -of cutting, and the slackening to a lack of some afferent stimulus -from the removed tissue. Conant obtained the same results on -Polyclonia by removing the oral arms (see Polyclonia) but says -nothing about a slackening of the rhythm in Charybdea. I believe -the increased rhythm in Charybdea was in part due to the decreased<span class="pagenum"><a name="Page_15" id="Page_15">[15]</a></span> -amount of labor necessary to force the water out of two openings -instead of one, namely, past the velarium. Just how much this -observation bears upon Romanes’ theory of rhythmic contraction, -that the rhythm is due to an alternate exhaustion and recovery of -the contractile tissue, as opposed to the ganglionic theory of rhythm -of physiologists, one does not wish to speculate much. Yet, I feel -that the observation rather supports this theory. The tissue having -to do less work, would become less exhausted at each contraction and -require less time for recovery and hence have a more rapid rhythm.</p> - -<p>I here sum up Romanes’ theory in a few words. The ganglia -liberate a constant and comparatively weak stimulus, one perhaps -about minimal. This stimulus sets off the contractile tissue; but as -the tissue contracts and becomes exhausted the constant stimulus -becomes, in relation to it, sub-minimal, and it does not contract -again until it has recovered and the stimulus is again strong enough -to set it off. The ganglionic theory of rhythmic contraction supposes -that the ganglia liberate stimuli to the contractile tissue at successive -intervals. Romanes had this theory suggested to him by the rhythmic -contractions he succeeded in obtaining by subjecting deganglionated -bells to a continuous but weak faradic stimulus, or by placing them -into weakly acidulated water, or into 5 per cent. glycerine. Romanes -claims that his theory better explains muscular tonus and the -contraction of involuntary muscle. He does not, however, hold this -theory to the exclusion of the ganglionic theory, since only too often -does he speak in terms of the latter. He further brings in his -support the fact that the frog’s tongue, in which no ganglia have -been demonstrated, can be made to contract rhythmically when -subjected to a weak and continuous stimulus. He also calls attention -to the rhythmic contractions seen in the Protozoa, the snail’s heart, -etc. Finally, physiologists are much inclined to explain the rhythmic -contraction of the heart and other involuntary muscles, in part, at -least, as due to a property of the contractile tissue.</p> - -<p class="section"><i>Margin, Radial Ganglia, Nerve</i>—Experiments <a href="#exp18">18</a>, <a href="#exp21">21-23</a>, <a href="#exp30">30</a>.—Complete -removal of the margin did not stop pulsation; but the -removal of the radial ganglia stopped it permanently. While this -experiment seems to have been tried only once, yet, taking into -consideration the results of other operations, it would seem that the -principal centers of spontaneity reside in these ganglia. (It should<span class="pagenum"><a name="Page_16" id="Page_16">[16]</a></span> -here be remembered that the interradial ganglia were probably -removed at the removing of the margin.)</p> - -<p>Cutting the nerve in the eight adradii caused the <em>pedalia</em> to bend -inwards at right angles to their normal position but did not in the -least affect the coördination of the sides. When, however, the sides -were cut in the eight adradii to the base of the stomach, coördination -for the main part ceased, and each side pulsated in its own -rhythm.</p> - -<p>I have said that the principal centers of spontaneity reside in the -radial ganglia. Upon further thought this hardly seems warranted. -No doubt, among the principal motor centers must be placed the -ganglionic masses of the clubs, and the radial ganglia, together -with the homologous interradial ganglia, represent centers of equal -value. I speak of these two sets of ganglia as homologous, since -strictly speaking, they both belong to the margin, and the clubs at -whose bases they lie probably represent modified tentacles. Conant’s -experiments leave us in the dark as to the function of these ganglia. -Next in order, it would seem, are the ganglion cells in the suspensoria, -as is suggested by the contractions of an isolated side with a portion -of a suspensorium attached. (See previous head.) While we have -seen that the frenula and the velarium can contract by themselves, -yet, I find no evidence that these can impart their contractions -to any adjacent tissue.</p> - -<p>Conant’s results on cutting the nerve eight times and then -continuing the cuts to the base of the stomach are quite the same as -Romanes and Eimer obtained upon Aurelia. Romanes, however, -concludes that in his Sarsia, Tiaropsis, etc., coördination was broken -when only short incisions were made in the margin. Charybdea -appears, then, to agree with Aurelia rather than with the Hydromedusæ. -Yet, since Romanes at first obtained similar results to those -of Charybdea on Sarsia, but on further experimenting concluded that -coördination had really been destroyed at the first cutting, we cannot -speak with certainty that coördination had not been destroyed in -Charybdea before the cuts had been continued to the base of the -stomach. I say not with certainty, because the injury to the bell -being slight, coördination may have been maintained on the principle -of a simultaneously (simultaneous for the octants) alternate exhaustion -and recovery of the contractile tissue on the principle of Romanes’ -theory.</p> - -<p><span class="pagenum"><a name="Page_17" id="Page_17">[17]</a></span></p> - -<p class="section"><i>Stimulation.</i>—Romanes found when he stimulated a deganglionated -bell of a Hydromedusa, that it responded by a single contraction, -while that of a Scyphomedusa responded with several quite rhythmic -contractions. Charybdea in this respect agrees with the Scyphomedusæ. -Romanes’ results were also verified on Aurelia. (Experiments -<a href="#exp12">12c</a>, <a href="#exp15">15</a>, <a href="#exp50">50</a>, <a href="#exp51">51</a>.)</p> - -<p class="section"><i>Activity of Charybdea.</i>—In speaking of the activity of Charybdea, -I cannot do better than refer the reader to the notes. (Experiment -<a href="#exp41">41</a>.) Conant remarks in his dissertation what an active swimmer -Charybdea is, and this is further borne out by his later observations.</p> - -<p class="section"><i>Temperature.</i>—Ice in the water seemed to have no effect, except -when held against an animal, when a slowing of pulsation followed -in a few instances. On some pulsating actively in the sun the -temperature of the water was found to be 92° F. (Experiments <a href="#exp33">33-35</a>.)</p> - -<p>Conant does not tell us how cold the water became when he -placed ice in it, but judging from his results, it seems that he might -have obtained a decided slowing of pulsation if the water in which -the medusæ swam had been permitted to approach anywhere near -the freezing point, say 35-40° F. Romanes obtained decided slowing -of pulsation, and even complete inhibition, on a bell of Aurelia, as -also a lengthening of the latent period on some strips cut from a -bell of Aurelia, by lowering the temperature of the water. Replacing -Aurelia in warmer water had the effect of immediate recovery and -increased rhythm. In Aurelia, raising the temperature increased the -rhythm but diminished it when the temperature of the water became -70-80° F. After a slowing of pulsation due to such a rise of temperature, -it would not quicken again when the animal was placed in -water of its normal temperature. Romanes explains this by supposing -that the tissue of the medusa had been permanently injured by the -abnormally high temperature. It would be interesting to observe -how the tropical Aurelia behaved under such treatment, seeing that -Charybdea pulsated actively and without apparent injury in water at -92° F. <i>Limnocodium</i>, noted by Romanes, and probably a tropical -species, lived happily in water at 85° F. in the lily house of the Royal -Botanical Society. The temperature of the water could be raised to -100° F. before it proved fatal to this medusa. Such facts point to a -decided difference in the constitution of the protoplasm of tropical and<span class="pagenum"><a name="Page_18" id="Page_18">[18]</a></span> -temperate medusæ. Romanes’ Sarsia became frantic when placed in -milk-warm water.</p> - -<p>While writing the above, I was led to wonder whether the -temperature of the water may not have been the stimulating -influence in those experiments on light (previously noted) in which -the medusæ continued to swim actively in the sunlight.</p> - -<p class="section"><i>Food and Feeding.</i>—See Experiment <a href="#exp36">36</a>.</p> - -<p>I again make note of a few observations made by myself on -the Olindiad. A crustacean became entangled in the tentacles of a -medusa; apparently this wished to retain it, for the proboscis reached -in the direction of the crustacean, which, however, got away. I then -placed, by means of a needle, another small crustacean against one of -the tentacles. This was seized but not retained, for the animal -pulsated and it was washed away by the water. Twice I saw a good-sized -crustacean in the proboscis. In one instance the velum appeared -to hold the part of the crustacean not yet in the proboscis. I noticed -another with a crustacean wholly in the proboscis, which was much -lengthened out, the upper part of the crustacean being in the stomach. -The next morning the crustacean was wholly in the stomach and the -proboscis normal. At 5.30 <span class="smcapuc">P. M.</span> the crustacean was ejected, nothing -but the shell and some rubbish remaining.</p> - -<p>These medusæ seem to pay no attention to being touched by one -of their kind, except to give a pulsation or two.</p> - -<p>The proboscis appears very “intelligent” in its actions.<a name="FNanchor_3" id="FNanchor_3"></a><a href="#Footnote_3" class="fnanchor">[c]</a> First, -some of the tentacles can be seen to contract and to bend inwards, -then the side next the tentacles contracts and the proboscis is seen -to reach in that direction. I could not see, however, what the irritant -was.</p> - -<p class="section"><i>Occurrence of Charybdea</i>—Experiments <a href="#exp37">37-40</a>.—Dr. Conant’s remarks -(“Cubomedusæ”) on the occurrence of Charybdea at the surface of -quite shallow water and near the shore (which is quite at variance -with former observations, that the Cubomedusæ are essentially deep-sea -forms) are further borne out by his observations at Port Antonio. -As already noted in the Introduction, Charybdea was here found in -abundance in quite shallow water and near shore, but on the<span class="pagenum"><a name="Page_19" id="Page_19">[19]</a></span> -bottom instead of at the surface as at Port Henderson. It is possible -that the animals had been active near the surface earlier in the -morning and that some unknown conditions determined their settling -to the bottom earlier in the former place than in the latter.</p> - -<p>Conant’s conjecture, “whether these were their natural conditions, -or whether the two forms,” Charybdea and Tripedalia, “were driven -by some chance from the deep ocean into the harbor and there -found their surroundings secondarily congenial, so to speak,” -seems to be borne out in favor of the former supposition (for -Charybdea at least),—that these are their natural conditions and that -Charybdea Xaymacana is essentially a shore form.</p> - -<h3><span class="smcap">Aurelia and Polyclonia</span> (<span class="smcap">Cassiopœa</span>)</h3> - -<p class="center">Experiments <a href="#exp42">42-53</a>.</p> - -<p>Many of the observations on these forms relate to the rate of -pulsation. In an Aurelia, following the removal of a lithocyst, there -was a pause followed by pulsations. In about two minutes rhythmic -pulsations were renewed. Four minutes after the operation there -were nineteen pulsations to the half minute, while twenty minutes -after there were only nine, and these in groups of six and three. -The normal rate of pulsation was twenty-five to the half minute.</p> - -<p>Polyclonia behaved much in the same manner as Aurelia. Upon -the removal of lithocyst pulsations continued, but in groups with -short pauses. The normal rate of pulsation was twenty-seven to the -half minute, while three minutes after the operation it was -seventeen, and eleven minutes after, fifteen to the half minute. -The tissue connected with a removed lithocyst gave contractions. -Placing a Polyclonia in fresh sea-water more than doubled the -rate of pulsation, which, however, soon fell to the normal rate, and -lower in one instance. In small individuals the rhythm is decidedly -more rapid than in those of larger size. The few observations on -this point would seem to show that it is in inverse proportion to the -squares of the diameters of the bells.</p> - -<p>The removal of a single oral arm or of the whole eight, in -Polyclonia, had much the same effect as the removal of a lithocyst: -there was a decided slowing of the rate of pulsation, while the -immediate effect of cutting was an acceleration or a return to near -the normal rate. About a day later this same animal had quite<span class="pagenum"><a name="Page_20" id="Page_20">[20]</a></span> -regained its normal rate of pulsation and continued to live over two -weeks. A long latent period followed the cutting of an arm, before -the stimulation of cutting manifested itself.</p> - -<p>An Aurelia, with all its lithocysts removed, still gave spontaneous -and coördinated contractions after allowing time for recovery from -the operation. This was the result in one instance, while in several -others only a few contractions were observed. Removal of the -sixteen marginal bodies (lithocysts) in a Cassiopœa produced paralysis -for a time but recovery soon followed. A Polyclonia with its entire -margin removed was paralyzed but had so far recovered in a day -as to be able, at intervals, to give spontaneous pulsations.</p> - -<p>The removed margin of a Polyclonia pulsated vigorously. This -margin was then split so as to make a ring within a ring but -connected at one point by a small bridge of tissue. The waves of -contraction, which always originated on the ring with the lithocysts, -passed the bridge to the inner ring quite as Romanes experienced. -The outer ring was next split so as to separate the exumbral -portion from the subumbral, when it was found that the contractions -always originated from the latter. Seven days after its removal, -this same margin was still alive and pulsating vigorously, and -broken-off pieces of the subumbral portion were pulsating by -themselves. Fifteen of the ganglia were removed. It was then -found that while most of the pulsations originated at the remaining -ganglion, now and then contractions originated in other parts where -no ganglion remained. Two days later this margin was still alive -with contractions originating as often from other parts as from the -ganglion. A similar observation was made on a margin of Cassiopœa.</p> - -<p>A Polyclonia with the eight lithocysts of one side removed, to -compare with a normal one, gave no evidence of affected coördination.</p> - -<p>An oral lobe from an Aurelia could give contractions some -minutes after removal.</p> - -<p>In another Aurelia a circular cut was made about the base of -the oral lobes through the epithelium of the subumbrella. The -animal could pulsate well enough but coördination seemed a little -affected, while in another one with a like cut but semicircular, no -effect was noticed.</p> - -<p>These results on the removal of the lithocysts (and margin in -Polyclonia) in Aurelia, Polyclonia and Cassiopœa agree quite with -those on Charybdea and, of course, also with Romanes’ and Eimer’s<span class="pagenum"><a name="Page_21" id="Page_21">[21]</a></span> -results as to paralysis and recovery following the removal of the -lithocysts, or margin, in Aurelia, Cyanea, etc. I recall no similar -observations, however, on removing a single lithocyst, and the -question of an explanation for the slowing of the rhythm thus -brought about arises. Romanes gives as an explanation for the -slowing of the rhythm (Aurelia, Cyanea, etc.) following the temporary -acceleration upon removing the manubrium or a portion -from the center of the bell, as due to a lack of an afferent stimulating -influence upon the ganglia from the excised tissue. May a similar -explanation not serve to explain the slowing following the removal -of a single lithocyst, above noted? The removed lithocyst could no -longer give its efferent stimulus to the remaining ganglia nor to -the tissue, so that the former would have a weaker stimulating -influence, in consequence of which the latter (the contractile tissue) -would be deprived of a part of the original stimulus of the -remaining ganglia as also of that of the removed ganglion. The -whole would thus result in giving to the contractile tissue a weaker -stimulus, which, again, would require longer and greater recovery on -the part of the tissue in order to be set off by the stimulus at -hand. This explanation is given on the basis of Romanes’ theory -of rhythmic contraction previously explained.</p> - -<p>Of course, it may be suggested that the musculature had lost -tonus, due to the lack of influence of the removed ganglion (lithocyst), -in consequence of which there was a lowering of irritability on the -part of the contractile tissue. This would require a greater summation -of stimulating influence (Ganglionic theory of contraction) -on the part of the remaining ganglia to set it off. Again, the loss of -irritability on the part of the contractile tissue may have been due -to a lack of nutritive influence from the removed ganglion.</p> - -<p>Romanes’ explanation, that the slowing of the rhythm following -the removal of the manubrium and central parts of the bell in -Aurelia and Cyanea is due to a lack of an afferent stimulus on the -ganglia from the removed tissue, likewise explains the similar results -obtained by Conant by removing the oral arms from Polyclonia.</p> - -<p>The fact that a margin of Cassiopœa and also of Polyclonia, -connected with but one ganglion, often originated contractions in -other parts as well as from the ganglion, seems to show that -motor centers resided in the margin outside of the ganglia. This -would be somewhat at variance with Romanes’ conclusion, that no<span class="pagenum"><a name="Page_22" id="Page_22">[22]</a></span> -such centers existed in the Scyphomedusæ. Conant does not state -whether the Polyclonia margin in question was kept in fresh sea-water -or whether the water was not changed during the seven days. -If the latter is the case, then some poisonous compounds may have -been formed that acted as a stimulus much as weakly acidulated -water served Romanes in producing rhythmic contractions in -deganglionated bells.</p> - -<p>Again, while it is true that no ganglia are known to exist in the -margins of the Scyphomedusæ outside of the ganglia in the marginal -bodies, yet, ganglion cells and nerve fibers are found in the subumbral -part of the margin as well as in the rest of the umbrella. -And as I know no reason why scattered ganglion cells may not -function as ganglia, it is possible that the contractions in question -were spontaneous.</p> - -<p>Finally, is it possible that the remaining ganglion originated -the contractions in different parts of the margin, thus acting -at a distance from the points at which contractions originated? -Romanes gives an instance in which he believed to have evidence -that this was the case. Upon a final consideration I am inclined -to this latter explanation.</p> - -<h3><span class="smcap">Summary.</span></h3> - -<p>Summing up for Charybdea, we have seen that it is very sensitive to -light, strong light as also darkness inhibiting pulsations, while -moderate light stimulates it to activity. Also, a sudden change from -weaker to stronger light, or <i>vice versa</i>, may inhibit or stimulate to -activity respectively. This behavior of Charybdea seems to be -correlated with its habit of life on the bottom. We have no -reason to doubt but that the eyes of the sensory clubs are the seat -of light sensation.</p> - -<p>The experiments on equilibration are negative, giving us no -certain light on the function of the concretions, though it appears -that they may serve, in part at least, for keeping the sensory clubs -properly suspended. Their function in giving the animal sensations -of space relations is not, however, excluded.</p> - -<p>Excision of the sensory clubs demonstrates that they are the seat -of important ganglionic centers, the removal of which results in -temporary paralysis and weakness. That they also are the seat of -organs (eyes, network-cells, concretions) that are of importance in<span class="pagenum"><a name="Page_23" id="Page_23">[23]</a></span> -giving information in the life of Charybdea, is evident from the -reaching motion of the proboscis after the removal of the sensory -clubs. Other centers of spontaneity in their order of importance -probably are: the radial ganglia (one experiment); the interradial -ganglia (?); the suspensoria, as shown by their supplying stimuli to -isolated pieces of the sides connected with them; the frenula and the -velarium, the latter of which gave contractions when removed with -the frenula or in pieces only. No evidence is given that the frenula or -the velarium can impart their contractions to other tissue, though this -seems probable for the former. The proboscis can also contract of itself.</p> - -<p>Reflexes between the velarium, frenula, subumbrella, sensory clubs, -nerve, and any one pedalium, on the one hand, and the pedalia on -the other hand, are very common, and point to the pedalia with the -tentacles as organs of defense and offense. The pedalia serve also as -rudders in swimming.</p> - -<p>Finally, as judged by the results in this paper, Charybdea seems -to occupy, physiologically, a position intermediate between the -Hydromedusæ and the Scyphomedusæ. In its great activity as a -swimmer, in its response to light, and in its reflexes it is Hydromedusan, -while in the paralysis and recovery following the removal of -its marginal bodies, as also in its response with several pulsations -instead of one, when a deganglionated bell is stimulated, it is Scyphomedusan.</p> - -<p>The observations on the Discomedusæ, Aurelia, Polyclonia, Cassiopœa, -demonstrate the existence of motor nerve centers in the -marginal bodies; but that other centers are present is shown by the -recovery of pulsation following the removal of the marginal bodies -or the margin. These results are mainly confirmatory of those of -Romanes and Eimer. They differ from these in the fact that margins -of Polyclonia and Cassiopœa, with only one ganglion attached, -originated contractions distant from the ganglion. Removing of a -single lithocyst resulted in a slowing of pulsation, as did also the -removal of the oral lobes, though the immediate effect in the latter -case was an acceleration. Isolated pieces of the subumbrella could -contract.</p> - -<hr /> - -<h2 id="DR_CONANTS_NOTES">DR. CONANT’S NOTES.</h2> - -<p>Below follow Dr. Conant’s notes. They are printed about as -Conant left them. Their order of succession, however, has been<span class="pagenum"><a name="Page_24" id="Page_24">[24]</a></span> -changed to bring similar experiments together, while useless and -often repeated ones have been omitted, and short elliptical sentences -completed. Where the present writer wished to add any explanation, -the same has been placed in brackets.</p> - -<h3><span class="smcap">Charybdea.</span></h3> - -<p class="section" id="exp1"><i>Light and Darkness.</i>—1. Eight medusæ, in a deep glass jar and -covered by a black coat, except one inch around the top, were -placed in the dark-room.</p> - -<p>a. When light from a lamp was thrown on the surface (one -inch) layer, the animals were active near the surface; when the -light was withdrawn, one or two were on the bottom and not moving -but were probably pulsating.</p> - -<p>b. After four or five minutes in the dark, three or four besides a -feeble one are on the bottom. It took about two minutes to get them -all to swim [by the lamp]. Of the three on the bottom, one, at any -rate, was not pulsating. [Three other attempts like a and b were -made, with very similar results.]</p> - -<p id="exp2">2. Experiment No. <a href="#exp1">1</a> was repeated several weeks later. Four in -a large round glass dish were placed in the dark-room. A lamp -being held to the dish all but one were found to be on the bottom. -That one quickly went to the bottom, while two of those on the -bottom quickly came to the top. In two or three minutes the one -that had gone to the bottom began to pulsate and at about the -same time the other one that had remained on the bottom also -began to pulsate, while the two that had gone to the top stayed -there swimming very actively. [Repeated with like results.]</p> - -<p id="exp3">3. Fresh ones did not show the reaction to light after darkness -so well as did those in the experiments previously recorded. They -were experimented with about nine <span class="smcapuc">A. M.</span>, while usually they were -tried later in the day. I had rather suspected from previous work -that they would not react so well when fresh.</p> - -<p id="exp4">4. a. In walking with the jar (1) of jelly-fish of experiment <a href="#exp1">1</a> -from the dark-room to the back porch of the laboratory (fifty steps), -in the bright sun and a cool breeze, all were found upon entering -the laboratory door to have settled to the bottom and most of them -to have ceased active swimming. In five minutes two or three were -swimming somewhat, and in five minutes more all but one or two -(eight in all) were swimming.</p> - -<p><span class="pagenum"><a name="Page_25" id="Page_25">[25]</a></span></p> - -<p>Walking with the jar about the laboratory did not suffice to -make any change in their swimming, nor did blowing on the surface -make any appreciable change.</p> - -<p>b. Upon taking the jar to the back porch and placing it on the -stone or cement flags, in the shade and a cool breeze, in four -minutes time all were on the bottom not even pulsating.</p> - -<p>Upon replacing them on the laboratory table all began to swim -about at once. [Repeated.]</p> - -<p>c. The jar (1) was placed on the back porch again; in fifteen -seconds three were on the bottom; in one-half minute all but one. -In three or four minutes all were on the bottom, but two were -swimming lively and the others pulsating. In another minute all -were swimming.</p> - -<p>d. The jar (1) was tried again, not resting it on the flags but -holding it by my hands on the sides. The effect was just as quick; -they stopped pulsating at once. By the time I had got back to my -table in the laboratory, one was at the surface and another arrived -just as the jar was set down.</p> - -<p>[Several other experiments of an order similar to those just noted -were tried, with very similar results.]</p> - -<p id="exp5">5. Two buckets stood side by side in the laboratory. One bucket -(1) had more Charybdeas in it than the other bucket (2), and also -had more since brought in (about an hour). The water of one (1) -was also more discolored and with more organic matter (sea weed, -etc.). In the laboratory the animals were active on the surface of -both buckets. Placed in the sunlight on the porch, no breeze, the -sun slanting so that one side of the water in the buckets was -bright while the other side was shaded, the jelly-fish in (1) went -mostly to the bottom, while those in (2) seemed unaffected though -some showed a tendency to go to the bottom after a longer -exposure. The experiment with (1) was repeated and it took some -five minutes for them all to go to the bottom. In a few minutes -after replacing them in the laboratory several were active again on -the surface.</p> - -<p id="exp6">6. Jar (a) with five large ones stood on my table; they were quite -active. Placed in the sun (no breeze), on the porch, one or two sank -to the bottom at once and the others seemed to slow their activities -somewhat but not very markedly. In a few minutes all were swimming, -apparently more actively than before, in the bright sunlight.</p> - -<p><span class="pagenum"><a name="Page_26" id="Page_26">[26]</a></span></p> - -<p>[In other experiments Conant shows that it is not the stimulus -of walking that causes them to swim when carried into the room, -for they would not swim when he walked with them on the porch. -Also, he shows how they may change, some swimming, others not, -when left for some time in any one place.]</p> - -<p id="exp7">7. In a tumbler were two pulsating very vigorously. Placed in -the bright sunlight, very little breeze now and then, they showed no -change whatever.</p> - -<p id="exp8">8. Some in a jar were covered with a black coat. The coat was -taken off, and almost immediately they stopped pulsating, or pulsated -but feebly, and sank to the bottom. The coat was put on again with -one part near the bottom of the jar exposed. Almost at once, the -animals, which were quite motionless, pulsating but little, resumed -pulsation, which became more and more vigorous, and quickly swam -to the top again. It seems plainly to be a reaction to light. [Such -experiments as this were repeated at different times with very like -results.]</p> - -<p id="exp9">9. A bucket with several bobbing actively on the surface was set -out in a smart shower, and the animals continued bobbing on the -surface as before. I could not see that they made the slightest -attempt to go below.</p> - -<p>There can be no doubt but that there is an individual difference -in sensitiveness to the reaction of light after darkness. E. g., I just -removed the coat from a dish with four in it; one went to the bottom -at once, another presently, a third remained active at the surface, -the fourth when noticed was on the bottom.</p> - -<p>There is also a difference in the length of time they stay on the -bottom as well as in the quickness in the response to light. Some -recover very quickly, should say in less than a minute, and at once -become very active. Some stay for a long time and only resume -activity upon the coat being placed over them. Perhaps this explains -some of the observations in Experiment <a href="#exp1">1</a>.</p> - -<p class="section" id="exp10"><i>Sensory Clubs.</i>—10. All four concretions were removed and the -animal stood the operation well. It swam more restlessly, however, -than others did in the same surroundings. It seemed at first to show -a trace of loss of sense-perception. It swam up, and down again, -more changeable than those intact, which stay rather more constantly -either on the bottom or at the surface. This may, however, have been<span class="pagenum"><a name="Page_27" id="Page_27">[27]</a></span> -due solely to the restlessness of the animal after the operation. Later -it swam actively for by far the most part on the surface only, which -points to the truth of the preceding statement.</p> - -<p>It showed no reaction to <em>light</em>. A coat placed over the jar was -removed, when it was found to be on the surface and it remained -there. This was twice repeated. I noticed specially that on pushing -the bell above the surface of the water it at once turned and went -deeper as the normal animal does. Finally, given another a trial with -removing the coat from the jar, it went to the bottom as the normal -animal usually does. After this, when next seen, it was keeping to -the bottom. [This experiment was repeated on another occasion with -almost identical results, no loss of sense-perception being noticeable.]</p> - -<p>Sometimes it seemed as if access of <em>light</em> at removing the coat -acted as a stimulus to one or more of those that were quiescent on -the bottom. This was noticed again on the following day.</p> - -<p id="exp11">11. Two more were operated upon. These did not stand the -operation well and stayed on the bottom, one swimming, while eight -hours later one was in better condition (pulsating) than two left in -the same dish for comparison.</p> - -<p id="exp12">12. a. Three clubs were cut off leaving only the stalks. A -temporary paralysis of the power to swim was the immediate effect. -Later it partially recovered this power. The proboscis, which was -previously quiet, now showed convulsive twitchings and movements. -It continued for some time to move to one side and then the other -(after short pauses of varied length) as if to grasp some object. -The lips of the <em>proboscis</em> were also moving and at times expanding. -Often the movements were towards the side on which the club was -uninjured.</p> - -<p>b. The fourth club was next removed. A temporary paralysis -as before resulted, followed by a quick recovery of pulsation; but -the animal was now much weakened. The movement of the -proboscis continued—shortening, lips expanding, moving to this side -or that. The pulsations of the bell were kept up even when too -weak to swim.</p> - -<p>c. The sensory niches of this same animal were treated with 2.5 -per cent. acetic acid by means of a pipette. The stalks of all four -clubs showed white. Pulsations ceased. The velarium showed feeble -local contractions. The movements of the proboscis and suspensoria -drawing down the stomach continued. Upon stirring the animal it<span class="pagenum"><a name="Page_28" id="Page_28">[28]</a></span> -gave rather feeble, somewhat convulsive pulsations with local -(fibrillar) contractions; the pulsations in some cases were pretty well -coördinated, but were more on the twitching kind.</p> - -<p id="exp13">13. Three clubs were removed. The animal pulsated well, only -a little less strongly, perhaps. After a minute or two the fourth -club was removed. It pulsated almost immediately, perhaps thirty -seconds after the operation. It swam very well and pulsated feebly -five hours after the operation.</p> - -<p id="exp14">14. One from jar (a) (Experiment <a href="#exp6">6</a>) was operated upon. -When the first club was cut off there was a paralysis of pulsation -followed by a quick recovery. Cutting off the second club seemed -to stimulate pulsation, the third to diminish it; after cutting off -the fourth club it still pulsated. When placed in a large jar it -pulsated on the bottom, but not strong enough to swim. The -pulsations were fairly regular and sometimes seemed to occur in -groups of two, but these groups were not well marked.</p> - -<p id="exp15">15. Another one from jar (a) was taken. One club was cut out, -upon which there was a very temporary paralysis followed by good -pulsations afterwards. The <em>proboscis</em>, as in all cases noticed, gave -active movements to this side and that side. These movements of -the proboscis were often very quick and definitely directed as if a -well defined stimulus were given. After the operation one <em>pedalium</em> -contracted so as to be at a right angle to the main axis of the bell; -shortly a second pedalium also contracted. Placed in a small round -dish the animal swam actively.</p> - -<p>A second club was removed, and it swam as well as before. After -fifteen minutes it was not swimming but pulsating against the jar. -Upon stirring it a little it swam vigorously ten to fifteen strokes -and then stopped. It seemed weak and its movements appeared -not so definite, though this might be due to weakness.</p> - -<p>A third club was removed. The only change seemed to be -rather greater weakness.</p> - -<p>After about five minutes the fourth club was removed. Paralysis -of pulsation followed. It had the power to contract its <em>pedalia</em> -when these were rather vigorously stimulated with a needle. It -also gave one feeble pulsation when so stimulated.</p> - -<p id="exp16">16. The sensory clubs were removed from another. After removal -of the third one it still pulsated actively, but stopped completely and -apparently for good after the removal of the fourth club. Another<span class="pagenum"><a name="Page_29" id="Page_29">[29]</a></span> -one stopped pulsating apparently for good upon removing the third -club.</p> - -<p id="exp17">17. All four sensory clubs were removed from one, cutting as -high up as possible so as to remove the endodermal tract of nerve -fibers of the peduncle. It pulsated afterwards apparently the same -as if the stalks had been left intact.</p> - -<p id="exp18">18. A small piece surrounding a sensory club and including the -<em>margin</em> can contract by itself. The piece observed pulsated with -quick pulsations and rhythmically but intermittently. After a fresh -cutting away of such a piece, the portion of the <em>velarium</em> attached -was seen to contract rhythmically, while the rest of the <em>subumbrella</em> -was not so seen. The part of the subumbrella above the radial -ganglion that was cut off did not contract by itself. The same -portion of the velarium cut off did give contractions.</p> - -<p id="exp19">19. A sensory club with the surrounding region cut out pulsated -rhythmically; when the club was cut from the end of its stalk -pulsation stopped. This observation was repeated on another, and -contractions were seen after the removal of the club. A piece of -the <em>subumbrella</em> wall from the same animal gave contractions now -and then even after an hour.</p> - -<p id="exp20">20. The normal position of a sensory club seems to be with -the concretion almost at the lowermost end; often with it certainly -lowermost, but probably oftener with the perpendicular passing -through the center of the attachment of the club to its peduncle -and just by the inner edge of the concretion. The eyes point inwards.</p> - -<p>When the animal is on its side the concretions are always quite -lowermost. When the animal was inverted the tendency was for -the concretions to be lowermost. In this position the eyes may -point in several directions. In one instance those of one club pointed -rather outwards, while of two other clubs they pointed more in the -plane of the body wall. (See also Experiments <a href="#exp24">24</a>, <a href="#exp29">29</a>.)</p> - -<p class="section" id="exp21"><i>Nerve.</i>—21. Cutting the nerve eight times, once on each side of -each sensory club, produced no loss of coördination in pulsating. -The animal was weakened, however, by the operation, which was made -drastic to insure cutting the nerve; but it was still able to swim. -This experiment was repeated four times.</p> - -<p id="exp22">22. That coördination was continued after the nerve was cut -was proved beyond doubt by cutting from the edge up (eight times)<span class="pagenum"><a name="Page_30" id="Page_30">[30]</a></span> -so as to perfectly separate the sensory clubs and the pedalia. -Pulsations continued synchronously in all four sides—not the -slightest evidence that one side contracted out of time with the -others.</p> - -<p id="exp23">23. The eight cuts were made as in the preceding experiment -with no loss of coördination noted. When the cuts were carried up -to the base of the stomach, however, coördination ceased. The four -side pieces seemed to contract each in its own time. Only two sides -could be observed at one time, and they at any rate did not contract -synchronously. One side often gave two contractions while the -other side rested or gave one.</p> - -<p>Yet, a little later, three of the sides at any rate showed a -pretty good coördination. The fourth was smaller and did not seem -to get into the game much—it went more on its own schedule. -The four pieces were then cut apart and placed together under a -dissecting microscope. No coördination at all could be made out. -No evidence, therefore, of any definite rate of pulsation inherent in -the sensory clubs.</p> - -<p>Cutting the nerve causes the <em>pedalia</em> to forcibly contract inwards.</p> - -<p class="section" id="exp24"><i>Side, Subumbrella.</i>—24. A whole side was cut out, the transverse -cut being above the sensory organ so as to take off [leave off] the -radial ganglion also. This pulsated, or rather contracted, nicely. -The upper end had been cut just through the <em>suspensorium</em>. It -especially gave twitchings like the twitchings of the stomach. The -piece was then halved transversely, when the upper part containing -the portion of the suspensorium twitched as before while the lower -part was not seen to contract again. This was repeated with the same -result, except that a portion of the lower part gave a slight contraction -several times. The part that contracted was at the upper end of the -piece, <i>i. e.</i>, nearest the <em>suspensorium</em>. The contractions were also more -longitudinal than transverse, as the regular contractions would be.</p> - -<p>The piece connected with the sensory clubs of course pulsated -nicely. Upon cutting off the sensory club from the stalk, pulsation -ceased, but twitching of the <em>velarium</em> continued. This was repeated -with the same effect.</p> - -<p>In the same animal, in cutting off the sides, the stomach was -left, the cut being through the gastric ostium. The floor of the -<em>stomach</em> was now cut off by cutting out the four interradial points of<span class="pagenum"><a name="Page_31" id="Page_31">[31]</a></span> -attachment. The stomach and the proboscis gave vigorous contractions -and tied themselves all up so that I could not cut off the -proboscis.</p> - -<p>The four pieces of the floor of the stomach left on the interradii -gave contractions nicely. The phacelli continued their squirming -movements.</p> - -<p id="exp25">25. Cutting off the whole aboral end of the animal excites to -very rapid pulsations of the remaining part. The stream, as shown -by particles in the water, is apparently stronger out the aboral end -than past the velarium.</p> - -<p>It seems that I get no good evidence that the subumbrella is able -to contract of itself without connection with special nerve centers. -In the one case noted (Experiment <a href="#exp31">31</a>) I could not be sure but that -the part that contracted was intimately associated with the suspensorium -or frenulum.</p> - -<p id="exp26">26. A piece of the subumbrella cut off and having, so far as I -could determine, no connection with ganglia, frenula, or suspensoria, -gave contractions. Another piece was not seen to contract.</p> - -<p>A small piece of the subumbrella connected with a club can contract. -The proboscis can give contractions of itself when cut off with the -base of the stomach. Even a cut-off lip can twitch by itself. A -portion of the subumbrella by itself also showed twitchings. (See also -Experiments <a href="#exp18">18</a>, <a href="#exp19">19</a>, <a href="#exp25">25</a>, <a href="#exp26">26</a>, <a href="#exp29">29</a>, <a href="#exp47">47</a>, <a href="#exp49">49</a>.)</p> - -<p class="section" id="exp27"><i>Pedalia, Velarium, Radial and Interradial Ganglia.</i>—27. The pedalia -with their tentacles were cut off at their bases to insure cutting out -the interradial ganglia. The animal could pulsate well enough, but -intermittently and without much progress (the velarium, of course, -being injured). Cutting one pedalium caused the others to contract.</p> - -<p id="exp28">28. When the pedalia were cut off from one, the power of direct -motion was entirely gone. It swam in circles, turned summersaults, -changed its course continually, the oral end getting ahead of the aboral -end, or trying to do so. The whole power of balancing was gone. It -seemed excited by the operation and swam continually. [Repeated.]</p> - -<p id="exp29">29. The pedalia can be made to contract inwards by stroking their -outer edge with a needle. This was noted last year and has been -seen several times this year. Their inner edge is not so sensitive.</p> - -<p>Touching a <em>sensory club</em> caused the pedalia to contract inwards in -two cases.</p> - -<p><span class="pagenum"><a name="Page_32" id="Page_32">[32]</a></span></p> - -<p>The pedalia could be made to contract by giving the subumbrella -a prick,—generally a rather severe one was necessary. The upper -part of the subumbrella seems not so sensitive as the lower part and -the proboscis, and the base of the stomach did not give any reflex -at all (two specimens). One of the two could be made to give the -reflex only with much difficulty. This was a very lively one. It -would even stand severe pricks on the nerve, or even through the -region of the sensory clubs, without contracting the pedalia or stopping -pulsations.</p> - -<p>Cutting the frenula seemed not to affect the ability to swim well. -Cutting in this region brings about the reflex of the pedalia.</p> - -<p>In the preceding fish the <em>velarium</em> was cut away wholly in some -places, in other places it was left only as ragged strips. The pedalia -became very strongly contracted and the <em>tentacles</em> were brought inside -the bell. Pulsations that seemed strong produced much less progress -than with the velarium intact. [Repeated.]</p> - -<p id="exp30">30. One with the whole <em>margin</em> cut off still gave pulsations. Upon -the removal of the region of the <em>radial ganglia</em>, however, pulsations -were seen no more.</p> - -<p>The <em>velarium</em> in the above continued to give twitchings. The four -pedalia were cut off with plenty of the tissue at their bases to insure -the removal of <em>interradial ganglia</em>, and twitchings of the velarium with -irregular contractions continued. No full contraction all around the -velarium was noticed. When all the tissue was trimmed off as nearly -as possible down to the <em>velarium</em>, the latter still gave twitchings and -irregular contractions as before,—even more so as if excited by the -operation. The power of originating contractions evidently resides in -the velarium or in the ganglion cells of the frenula just as it does in -the proboscis and the floor of the stomach.</p> - -<p>Small pieces cut from between the pedalium corners and the -frenula, so as to have tissue on them from neither, could contract -by themselves. (See also for Pedalia, Experiments <a href="#exp15">15</a>, <a href="#exp23">23</a>, <a href="#exp41">41b</a>; -Velarium <a href="#exp18">18</a>, <a href="#exp41">41c</a>.)</p> - -<p class="section" id="exp31"><i>Tentacles.</i>—31. A cut-off tentacle can contract by itself, sometimes -with squirming contractions. A prick at either end can produce a -forcible contraction. A slight prick at the distal end may produce a -local contraction. The proximal end is more sensitive, but this difference -is not very marked. One with only the tentacles removed -seemed to be a little less able to guide itself well.</p> - -<p><span class="pagenum"><a name="Page_33" id="Page_33">[33]</a></span></p> - -<p class="section" id="exp32"><i>Proboscis, Stomach, Phacelli.</i>—32. The lips of the proboscis are -highly contractile by themselves. The movement of the stomach and -the phacelli goes on, after the lips are cut off, with increased vigor, -due to the stimulus of shock. The vigor and frequency of their -contractions, however, diminish quicker than that of the cut-off lips. -(See for Proboscis, <a href="#exp12">12</a>, <a href="#exp15">15</a>, <a href="#exp18">18</a>, <a href="#exp26">26</a>, <a href="#exp29">29</a>; Stomach, <a href="#exp18">18</a>, <a href="#exp24">24</a>, <a href="#exp29">29</a>, <a href="#exp31">31</a>; Phacelli, -<a href="#exp18">18</a>, <a href="#exp24">24</a>, <a href="#exp31">31</a>.)</p> - -<p class="section" id="exp33"><i>Temperature.</i>—33. Temperature does not seem to have much effect. -Some placed in a tumbler half full of water, in the bright sunlight, -swam vigorously over three-fourths of an hour. The water was quite -warm to the hand.</p> - -<p id="exp34">34. The above experiment was repeated with the same results. -A thermometer placed in the water with them showed 92° F.; hung -in the sun near by, it showed 94° F.</p> - -<p>Ice in the water did not stop their pulsating temporarily or -permanently, except that it did for a short time after being held -against one. Even then it took some time (fifteen to twenty -pulsations) before it produced any effect.</p> - -<p id="exp35">35. Ice placed in the water again showed no marked effect. They -swam as lively as ever. Some, after pulsating against the ice for a -little while, seemed to be less vigorous, but quickly recovered in -another part of the jar. Others did not seem to be the least bit -affected by contact with the ice.</p> - -<p class="section" id="exp36"><i>Food and Feeding.</i>—36. I tried to feed one. A red and a white -copepod were put into the subumbrella cavity. No attempt to eat it -was observed in either case, though the copepods remained in the -subumbrella cavity for some time.</p> - -<p>Animals found in the stomach of Charybdea: small fish were -most frequently seen; at another time a small stomatopod; again, a -small polychæte; small shrimps; amphipod.</p> - -<p>Those taken on August 16th (3 to 4 <span class="smcapuc">P. M.</span>) seemed to have, for the -most part, food in the stomach, and this more so than those taken in -the morning.</p> - -<p class="section" id="exp37"><i>Occurrence of Charybdea.</i>—37. In the first tow on the bottom -(with a net made of mosquito-netting and weighted with rocks in -order to sink it) the haul was forty. I do not think that we could -have been towing more than four or five minutes. The time was<span class="pagenum"><a name="Page_34" id="Page_34">[34]</a></span> -about seven <span class="smcapuc">A. M.</span> A light breeze was blowing and there had been a -heavy shower a half-hour previous.</p> - -<p id="exp38">38. The usual time of towing was about 6.30 to 7.30 <span class="smcapuc">A. M.</span> The -water was four to five feet (1.2 to 1.5 m.) nearest shore but deeper -farther out. At this time of day one could count on getting plenty -of the larger sized (15 to 20 mm.), many small ones, but very few of the -smallest. This was the experience of several mornings.</p> - -<p>On August 12th I towed about nine <span class="smcapuc">A. M.</span>, and got but few of the -larger sized, many small ones, and very many of the smallest.</p> - -<p>The next day (7.00 to 7.45 <span class="smcapuc">A. M.</span>) those obtained were mostly of -the larger size. On the same day (3 <span class="smcapuc">P. M.</span>) others of the party towed -at the same place and obtained but few.</p> - -<p>On another day I towed in the afternoon (3 to 4 <span class="smcapuc">P. M.</span>) and -obtained great numbers as I usually did in the morning.</p> - -<p id="exp39">39. We towed about 7.30 to 8.30 at night. Very few Charybdeæ were -taken. On this evening we towed five times in the same locality, -and obtained but seven or eight specimens. Towing with the same -net on our way home, it was filled with Aureliæ and five or six -Charybdeæ. It seems as if Charybdea came to the surface at night. -Those towed in the evening were dead the next morning.</p> - -<p>The next morning Richard, our colored attendant, towed from -5.30 to 6.30. There were heavy showers. The usual find of large and -medium ones was obtained. There were only two with planulae.</p> - -<p id="exp40">40. The material of September 2nd was obtained about six <span class="smcapuc">A. M.</span> -They were mostly of large size. In all only fifteen or twenty were -taken. Richard explained the small number by saying that the -bottom had changed in the locality where we usually towed and that -he got no weeds in his net, but mud.</p> - -<p>The next day more were brought in by Richard (6.30 <span class="smcapuc">A. M.</span>) -There were rather more than yesterday but the quality was the same. -There were three with planulae.</p> - -<p>On another morning Richard brought in a great many, about a -hundred. Among these there were three with planulae (light-colored -and budding); on a previous day there was one with the reddish-brown -kind and with a mouth.</p> - -<p class="section" id="exp41"><i>Activity of Charybdea.</i>—41. a. About five o’clock in the morning a -Charybdea was taken in the tow. It was in good condition -swimming incessantly round and round without change of direction,<span class="pagenum"><a name="Page_35" id="Page_35">[35]</a></span> -in a jar of about twenty centimeters in diameter. It came to the -surface every now and then, after eight to fifteen pulsations. The -tentacles and the phacelli were of a lilac shade. If a pencil was -placed in its way it would pulsate against it repeatedly without any -effort to dodge around it.</p> - -<table summary="Results of the observations"> - <tr> - <td class="right">6.58</td> - <td><span class="smcapuc">A. M.</span>,</td> - <td>124</td> - <td>pulsations</td> - <td>were</td> - <td>counted</td> - <td>to the</td> - <td>minute.</td> - </tr> - <tr> - <td class="right">8.00</td> - <td class="center">“</td> - <td>124</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - </tr> - <tr> - <td class="right">9.25</td> - <td class="center">“</td> - <td>136</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - </tr> - <tr> - <td class="right">10.15</td> - <td class="center">“</td> - <td>131</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - </tr> - <tr> - <td class="right">11.00</td> - <td class="center">“</td> - <td>146</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - <td class="center">“</td> - </tr> -</table> - -<p>At 10.15 it went around the dish in eight seconds, taking eighteen -or nineteen pulsations. If a bright platinum spatula or a black -pencil was placed in its circuit it would repeatedly butt against -it each time it came around. After the second or third pulsation -against it, however, it seemed to have some sense to change its -direction.</p> - -<p>b. The <em>pedalia</em> have no perceptible action of their own. They -move inwards slightly toward the axis at each pulsation, but -scarcely as much as one would suppose from their attachment to -the pulsating margin. It seems as if they were for “winging” the -moving animal more than for anything else.</p> - -<p>c. The <em>velarium</em> is loose and it flaps. It seems to take part in -swimming something more than the passive diaphragm function,—i. e., -it straightens out during the recovery after each contraction of -the bell.</p> - -<h3><span class="smcap">Aurelia and Polyclonia.</span></h3> - -<p>[The following experiments were performed at Port Henderson, -Jamaica, in 1896.]</p> - -<p id="exp42">42. May 12th. An <i>Aurelia</i> was pulsating normally at the rate -of twenty-five or twenty-six pulsations to the half-minute. One -lithocyst was cut out, when a few contractions, evidently caused by -the stimulus of cutting, followed; then, rest. In the first minute -there were only about five pulsations. In two or three minutes -rhythmic pulsations were resumed. Four minutes after the cutting -there were nineteen pulsations to the half-minute. About twenty -minutes after there were nine to the half-minute, in groups of six -and three.</p> - -<p><span class="pagenum"><a name="Page_36" id="Page_36">[36]</a></span></p> - -<p>A <i>Polyclonia</i>, about four and one-half inches (115 mm.) in diameter, -gave twenty-six or twenty-seven regular pulsations to the half-minute. -After one otocyst was removed, pulsations continued, but in -groups with intervals of pause: <i>e. g.</i>, thirteen, pause; ten, pause; six. -Three minutes after the removal of the lithocyst there were 5, 3, 1, -3, 5, or seventeen pulsations to the half-minute. Eleven minutes -after the operation there were fifteen to the half-minute. The -removed lithocyst and surrounding tissue gave contractions.</p> - -<p id="exp43">43. May 13th. The <i>Aurelia</i> was in rather poor condition but -would pulsate upon being stirred. The other seven lithocysts were -removed when only a few contractions originated thereafter.</p> - -<p>The <i>Polyclonia</i> was in good condition, but was pulsating only -intermittently when first seen in the morning. When the remaining -seven lithocysts were cut out and no more pulsations were observed, -the oral arms could still move.</p> - -<p>May 14th. Both were found dead upon returning in the evening.</p> - -<p id="exp44">44. May 15th. An Aurelia and a Polyclonia were taken in the -morning. The <i>Aurelia</i> was two and one-half to three inches (62.5-75 -mm.) in diameter, with three tufts of phacelli, three oral arms and -seven lithocysts. The <i>Polyclonia</i> was normal and seven or eight -inches (175-200 mm.) in diameter.</p> - -<p>In the <i>Aurelia</i> all the lithocysts were removed. Spontaneous and -coördinated contractions could still occur after time had been allowed -for the shock from the operation to pass away. The next day the -animal was still alive and pulsating, but ragged, and the next day -following was quite dead.</p> - -<p>In the <i>Polyclonia</i> the normal rhythm was fourteen pulsations to -the minute. Some pulsations were apparently quicker than others -and the intervals were not the same. Thirteen, ten, and twelve -pulsations were also counted. After putting the animal into fresh -sea-water, it pulsated thirty-three to the minute. Six minutes later it -was still pulsating at the same rate, while in four minutes more -eleven pulsations, many of which were in groups of two, were noted. -In five minutes more it pulsated eleven times to the minute with -only one double pulsation. One <em>oral arm</em> was then cut off and the -rhythm counted about one minute afterward—fourteen pulsations, -then a pause of fifteen seconds, then two pulsations, in all sixteen to -the minute were counted. About ten minutes later there were eight -pulsations, two or three minutes later only three, while in two or three<span class="pagenum"><a name="Page_37" id="Page_37">[37]</a></span> -minutes more only three. There was a long latent period—two or -three seconds—before the stimulation of cutting off the arm made -itself evident in the rhythm.</p> - -<p>A second oral lobe was removed. Then there followed twenty-four -pulsations, a pause of two seconds, and two pulsations, in all twenty-six -pulsations to a minute. The rate of pulsation soon fell to the -previously abnormal low rate.</p> - -<p>Third lobe removed: 21 pulsations in first half minute and then -16, or 37 per minute.</p> - -<p>Fourth lobe removed: 17 pulsations in first half-minute plus 13 -gives 30 for the minute.</p> - -<p>No difference in the coördination of the animal was shown as a -result of the removal of one-half the number of oral arms.</p> - -<p>Fifth lobe removed: 17 pulsations plus 15 equals 32 to the minute.</p> - -<p>Sixth lobe removed: 17 in first half-minute plus 4 in the second -half-minute gives 21 pulsations for the minute.</p> - -<p>Seventh lobe removed: 17 plus 9, or 26 per minute.</p> - -<p>In all these instances the rhythm in the second half of the first -minute was irregular and intermittent.</p> - -<p>Seventeen and then seven pulsations were provoked after the -animal had become quiescent, or nearly so, by merely handling it.</p> - -<p id="exp45">45. Eighth oral lobe was removed and pulsations stopped. The next -day the animal was in good condition. The pulsations counted in the -evening were 12, 14, 14, 11, per minute. The rhythm was not -regular; there was a tendency to groups of twos, threes, or more, but -no prolonged intervals of rest were observed. When placed into -fresh sea-water, the pulsations were fourteen to the half-minute or -twenty-six to the minute; seventeen to the half-minute, and thirty-three -to the minute were also counted. This specimen gave spontaneous -contractions during two weeks, after which it was thrown -out, the aboral end being eaten through and little or no regeneration -having taken place.</p> - -<p id="exp46">46. Two more were operated upon: A. Its rhythm was 18, 14, 17. -Its entire margin was cut off. The separate pieces of the margin -pulsated, 6, 7, 4, 6, 7, 9. The animal seemed paralyzed by the -operation; it responded by a contraction now and then to stimulation -but gave no spontaneous pulsations. B. Its rhythm was 17, -15, 12, 12. All its <em>oral arms</em> were removed. Its rhythm was only -raised to seventeen and not perfect. In twenty-five minutes it had -fallen to eleven, in four hours to ten pulsations [per minute].</p> - -<p><span class="pagenum"><a name="Page_38" id="Page_38">[38]</a></span></p> - -<p>May 22nd. A and B are living as also the pieces of the <em>margin</em> -of A; all are giving spontaneous pulsations now and then at comparatively -long intervals—even A, with its margin removed.</p> - -<p>May 26th. Everything is still living. The one with the margin -cut (A) counted sixteen and nineteen pulsations per minute, though -this was not kept up all the time.</p> - -<p>June 2nd. A and B and pieces are still living and contracting -spontaneously. It is now two weeks, and they were thrown out eaten -through at the aboral end with little or no regeneration.</p> - -<p id="exp47">47. The margin was cut off another one (C) and it was then -paralyzed. The margin contracted vigorously by itself. The margin -was next split, but a connection of about one-half an inch wide was left -between the two rings. Over this bridge the contractions passed -from the outer and inner ring. The inner ring did not originate -any contractions. Both rings were then cut near their connecting -bridge of tissue and the larger ring with the marginal bodies was -split longitudinally so as to separate the exumbral from the subumbral -portion. It was found that the contractions started only from -the subumbral portion while the exumbral portion did not contract -at all.</p> - -<p>June 5th. Five of the eight small pieces of C were not seen to -contract either to-day or yesterday. A slow rotary motion was -observed in some of the pieces suggesting ciliation, but no cilia or -currents pointing to ciliation were seen with a low power. C was -seen to pulsate spontaneously. Possibly it did yesterday but it was -not watched closely. A piece of the subumbral surface of C broken -off (not from the margin) was found to contract spontaneously.</p> - -<p id="exp48">48. June 6th. In a fresh one (D) from Port Royal, the eight lithocysts -of one side were removed in order to compare its movements -with an intact one. Coördination was apparently unaffected.</p> - -<p>June 9th. The margin of C is still pulsating vigorously. Parts -of the subumbrella broken loose from the strip pulsated by themselves -now and then. Fifteen lithocysts were removed, leaving only -one at the end of the strip. It was found that with this single -ganglion (lithocyst) left, and originating most of the contractions, now -and then a contraction would originate at another part of the strip -where there was no ganglion. Three days later contractions -originated as often from other parts as from the ganglion.</p> - -<p><span class="pagenum"><a name="Page_39" id="Page_39">[39]</a></span></p> - -<h3><span class="smcap">Cassiopœa.</span></h3> - -<p>[The remaining experiments were all performed in 1897, at Port -Antonio.]</p> - -<p id="exp49">49. Removal of the sixteen marginal bodies caused paralysis for -a time; then recovery followed.</p> - -<p>Contraction was limited to the subumbrella.</p> - -<p>A portion of the <em>subumbrella</em> not from the margin can contract -by itself as well as a portion of the margin with the marginal bodies -(lithocysts).</p> - -<p>In the <em>margin</em> cut off as a strip with only one marginal body -attached at one end, contractions sometimes started from the opposite -end.</p> - -<h3><span class="smcap">Aurelia.</span></h3> - -<p id="exp50">50. Size, seventeen or eighteen millimeters. Pulsations, thirty-two. -Lithocysts, nine. The operation consisted in the removal of the -concretions with as little injury to the pigmented parts of the -marginal bodies as possible. One whole marginal body, however, was -removed in the operation. Soon after the operation the pulsations -were 28, 26, 20, 20, per minute.</p> - -<p>Another one; size fifteen millimeters. Pulsations were forty per -minute. The operation consisted in the removal of the concretions -and pigmented parts of the marginal bodies with as little injury to -the adjoining parts as possible. After the operation it seemed as if -the intervals between the pulsations were irregular,—not a series at -regular intervals. An hour or so after the operation the pulsations -were very intermittent. During the afternoon it was not seen to -pulsate except when it was stirred up, when six or seven vigorous -pulsations followed. These, however, were rather aimless.</p> - -<p id="exp51">51. One sensory club (marginal body) was cut out, including its -basal part also. In one or two other cases more or less injury was -done to adjoining parts also. Pulsations ceased upon the removal of -the last club, but upon placing it in an aquarium and allowing it to -come to rest for two or three minutes, pulsations were now and then -seen. In the evening, this one and another did not pulsate except -when stirred, when they pulsated with good progress.</p> - -<p id="exp52">52. A circular cut, about two inches in diameter, was made -through the epithelium of the subumbrella around the base of the<span class="pagenum"><a name="Page_40" id="Page_40">[40]</a></span> -oral lobes. The animal pulsated well enough, but the contractions -seemed not so simultaneous in all parts of the margin as normally. -After a few days it had partly regenerated but died. One of the oral -lobes cut off had some power of contraction, and this some time after -the operation. A similar cut, but semicircular, made no difference -between the contractions of the two halves.</p> - -<p id="exp53">53. The whole region of the sensory clubs was cut out when the -animal was not seen to pulsate again, except in the evening, when -pulsations were observed. The oral lobes also moved.</p> - -<hr /> - -<h2 id="HISTOLOGICAL">HISTOLOGICAL.</h2> - -<p class="section"><i>Method.</i>—The following results on the histology of the sensory -clubs, their eyes, and the tentacles, as already noted, were obtained -from some of Dr. Conant’s preserved material. These results relate -almost wholly to Charybdea, with only a few references to Tripedalia, -noted in their proper place.</p> - -<p>A portion of this material was killed after keeping the animals -in the dark for some time, for the purpose of discovering any -changes in the pigment of the eyes. I believe that a retraction -of the pigment of the long pigment cells that project between the -prisms and pyramids of the vitreous body in the retina of the distal -complex eye is very evident in eyes killed in the dark. (But more -on this below.)</p> - -<p>I obtained my best results from the material preserved in -saturated corrosive sublimate, to which had been added (5 to 10 per -cent.) acetic acid. This also was Conant’s experience in his previous -work on Charybdea and Tripedalia.</p> - -<p>My best sections were obtained by embedding the sensory clubs -in celoidin, passing the little blocks of celoidin with the sensory -clubs into chloroform until perfectly transparent, and then into -paraffine. I then cut sections as we ordinarily cut paraffine sections, -mounted and stained them on the slide. My purpose in using this -method was to avoid the displacement of the vitreous bodies of the -eyes during embedding and cutting. This object was fully realized -and more besides. Since the sections cut by the celoidin-paraffine -method gave me so decidedly the best differentiation of the axial -fibers of the retinal cells, as also of the cilia, basal bodies, etc., I am -inclined to believe that the celoidin was in part responsible for this -differentiation.</p> - -<p><span class="pagenum"><a name="Page_41" id="Page_41">[41]</a></span></p> - -<p>Most of my series were cut 4 µ in thickness. All in all I cut -sixty-five clubs besides making some maceration preparations from -material preserved for that purpose. These sixty-five series represent -material from fourteen bottles. As a whole, my material was good, -but the material from one bottle was decidedly superior for showing -the axial fibers of the prisms and pyramids of the retinal cells. -This shows the advantage of plenty of material. It will be evident -that I had plenty of material.</p> - -<p>I found iron-hæmatoxylin the most satisfactory stain. I stained -for a shorter or a longer time—one-half to several hours and longer—and -then washed out the sections until under a low power of magnification -they appeared quite unstained, the nuclei and a few other -parts only appearing darkly stained.</p> - -<p>Depigmentation I practiced but little. I obtained many of my -series almost wholly unpigmented, especially those I cut last. Others, -of course, were very heavily pigmented. I am not certain but that -alcohol slowly dissolves out the pigment after a long period of -preservation. Slight variations in the technique of killing and preserving -may also, perhaps, determine the stability or solubility of the -pigment, as, of course, also the condition of the pigment at the time -of killing.</p> - -<p class="section"><i>Anatomy.</i>—For a short epitome of the anatomy of a Cubomedusa -and of a Cubomedusan sensory club see <a href="#Page_2">p. 2</a> of the Introduction.</p> - -<p class="section"><i>The Distal Complex Eye</i>—<i>General</i>.—The distal (larger) complex eye -(<a href="#plate1">Fig. 7</a>) and the proximal (smaller) complex eye (<a href="#plate2">Fig. 13</a>) are so -named to distinguish them from the lateral simple eyes of the clubs. -The distal complex eye consists of the following parts: a cellular -cornea, continuous with the epithelium of the sensory club; a cellular -lens (externally cellular and internally often quite homogeneous) -immediately beneath the cornea; a homogeneous capsule just internal -from the lens, and evidently a secretion from the lens cells; a -vitreous body composed primarily of prisms and pyramids just -beneath the capsule; and a retina of pigmented cells, with subretinal -nerve tissue, ganglion cells and fibers. To my knowledge -all observers (except Carrière, who missed the capsule) are quite -agreed on the anatomical structure of the distal complex eye as also<span class="pagenum"><a name="Page_42" id="Page_42">[42]</a></span> -on the proximal complex eye and the lateral simple eyes.<a name="FNanchor_4" id="FNanchor_4"></a><a href="#Footnote_4" class="fnanchor">[d]</a> It is on -the histological structure of some of the various parts that differences -exist.</p> - -<p class="section"><i>Cornea.</i>—Little need be said on the cornea except that it consists -of flattened cells applied to the outer surface of the lens. It is -continuous with the epithelium of the club and evidently a modified -portion of this epithelium (<a href="#plate1">Fig. 7</a>). All observers conform to this -statement.</p> - -<p class="section"><i>The Lens.</i>—The lens is of cellular origin, but in its interior the -cells are often so changed—absence of nuclei, cell walls, and protoplasmic -structure—as to make a mass quite homogeneous and -structureless. While this internal mass sometimes shows practically -no structure, yet at other times it is found broken up into masses -much the size and shape of cells but without nuclei, while again, -cells with nuclei may be quite evident. This occasional breaking -up of this mass is evidently predetermined by its original cell -structure. Iron-hæmatoxylin stains this inner mass very dark and -it is difficult to wash out the stain. Borax carmine and Lyons -blue give the best results on the lenses. In <a href="#plate1">figure 7</a> the lens of -the distal complex eye is shown as quite homogeneous internally, -while in <a href="#plate2">figure 13</a> (proximal complex eye) it is drawn cellular. In -this latter lens the inner cells are quite round and nucleated as -they may also appear in the distal eye. What I have said applies -equally to the lenses of both complex eyes, though the cellular -nature of the inside of the lens is more readily demonstrated in -the proximal eye.</p> - -<p>It appears that it is in younger specimens that the central mass -of the lens shows the cellular structure best, and that as the animal -grows older this structure is more and more lost until no trace<span class="pagenum"><a name="Page_43" id="Page_43">[43]</a></span> -of it remains. As concerns most of my series I could not well -determine which were from younger and which from older -individuals, yet, several series of quite small (5 mm.) and therefore -young animals, in which the eyes were so small that the lenses were -compassed into less than half a dozen sections, the cellular structure -of the lens was very evident.</p> - -<p>The external cells of the lens form a spherical shell (both complex -eyes) which, in section, shows as a hollow ring (Figs. <a href="#plate1">7</a>, <a href="#plate2">13</a>). The -thicker ends of these cells lie at the inner (toward the capsule) half -of the sphere and the cells taper toward the corneal surface, dovetailing -laterally with their immediate neighbors as also distally with -those from the opposite side of the sphere. The thicker inner ends -of the cells contain the large nuclei with nucleoli. At a point (* Figs. <a href="#plate1">7</a> -and <a href="#plate2">13</a>) on the inner (next the capsule) surface of the lens the cells only -approximate each other and thus leave a place which is easily -broken through, as is shown by portions (drops, probably representing -cells or portions of cells) of the mass within the lens becoming -squeezed out into the substance of the capsule and the vitreous body, -and found occasionally also among the cells of the retina. A -considerable portion of the inside of the lens may be found thus -squeezed out, and its path can often be traced. This phenomenon is -evidently brought about by a contraction of the shell of the lens -during fixation and before the inside of the lens has become -hardened.</p> - -<p>In origin the lens is evidently ectodermal, originating from an -ectodermal invagination which becomes pinched off as a hollow -sphere, the outer (<i>i. e.</i> next the cornea) half of which becomes the -lens, the inner half the retina (<i>i. e.</i> vitreous body plus the so called -retina). (See Retina.) The transition from retinal to lens cells is -quite readily made out at the lower side of <a href="#plate1">Fig. 7</a>, but the corresponding -structure on the upper left side is not so manifest. It is -further evident that the lens is again an invagination into this -sphere, and the point at which the lens cells approximate (where the -central mass of the lens may be squeezed out as above described) -represents the place of pinching off of the original lens-retina sphere. -It appears, then, that the lens is formed in the lens-retina sphere in -the following manner: The cells of the secondary invagination -going to form the lens begin to lengthen distally (<i>i. e.</i> toward the -cornea) during their invagination to form a hollow sphere, at the<span class="pagenum"><a name="Page_44" id="Page_44">[44]</a></span> -same time dovetailing with each other and budding off cells to form -the inside of the lens (Figs. <a href="#plate1">7</a>, <a href="#plate1">13</a>).</p> - -<p>At the lower side of the lens, near the margin of the retina, the -cells of the lens are slightly indented or pushed inwards (<a href="#plate1">Fig. 7</a>, ind.). -I believe this to be due to the weight of the lens in the normal -position of the club, when the lens rests against the margin of the -retina and the capsule and adjacent tissue.</p> - -<p>Anticipating the description of the retina, it may here be added, -that the retina is formed from the inner half of the lens-retina sphere. -The cells of this portion of the sphere become differentiated into -prism cells, pyramid cells, and long pigment cells, while laterally, -beyond the margin of the vitreous body, they are differentiated into -pigmented iris cells (<a href="#plate1">Figs. 7, 6a</a>).</p> - -<p>Above are my results on the lens. Haake<span class="fnanchor"><a href="#book2">[2]</a></span> speaks of the lens as -consisting of a cellular “Kern” with a covering of lamellated cells. -Carrière describes it as cellular and filled internally with a “Gerinsel,” -or coagulation. Carrière and Haake are each in part right. Claus -describes it as wholly cellular. Schewiakoff regards the lens as wholly -cellular, and like Claus has not noted that internally this cell -structure may be quite obliterated. Schewiakoff regards the lens and -retina as formed from an invaginated sphere, and shows the -transition from the lens cells into retinal cells as I have figured. -Conant also gives the structure of the lens for the complex eyes as -cellular but missed the change of structure that the interior of the -lens may undergo.</p> - -<p class="section"><i>The Capsule.</i>—The capsule of the lens (<a href="#plate1">Figs. 4, 7</a>) lies immediately -below (inward from) the lens. In structure it is homogeneous, except -for certain fibers from the long pigment cells of the retina that -traverse it, while sometimes also other fibers can be seen which, -possibly, are branches from the fibers just mentioned or continuations -from the fine fibers of the prism cells of the retina soon to be -described. I have, however, no evidence that the fibers from the -prism cells extend beyond the prisms in whose axis they lie. The -capsule lies very closely applied to the lens, never becoming separated -from it in sections, and is, hence, regarded as a secretion from the -lens cells. Just what its function may be is difficult to surmise. -The proximal complex eye possesses no capsule. I have thought, -however, that if the lens should be adjustable, the capsule might<span class="pagenum"><a name="Page_45" id="Page_45">[45]</a></span> -serve as a protection to the prisms of the vitreous portion of the -retina during the adjusting movements of the lens. (But more on this -below.) To my knowledge all previous observers are quite agreed -on the structure of the capsule. Carrière and Haake, however, -missed it altogether.</p> - -<p class="section"><i>Retina.</i>—While I have enumerated (following previous observers) -the vitreous body and the so-called retina as distinct parts, yet, as -the sequel will show, they are, histologically, different parts of the -same thing—namely the sensorium proper of the eye—and I propose -to use the term retina for both taken together, while I retain the -expression vitreous body (as hitherto used) for the vitreous portion -of the retina. This simplifies matters; and using a word that is -already used for analogous structures of other eyes (vertebrates, -anthropods, molluscs) is conducive to clearness. I have been tempted, -furthermore, to use the words <em>rods</em> and <em>cones</em> for the prisms and -pyramids that I find in the vitreous bodies of the retinas of the complex -eyes. But since the prisms in reality approximate prisms and the -pyramids pyramids, in their shape, I have decided to retain the -words prism and pyramid for these structures. The former of these -terms (prism) was first used by Conant in his description of the -complex eyes.</p> - -<p>What I shall call the retina, then, in the distal and proximal -complex eyes of Charybdea, consists of three kinds of elements: -the prism cells, the pyramid cells, and the long pigment cells. (Figs. -<a href="#plate1">4</a>, <a href="#plate1">7</a>, <a href="#plate2">22</a>, prc, pyrc, lp.) We may also describe the retina as composed -of three zones: the vitreous zone (vitreous body of authors), -the pigmented zone, and the nuclear zone. (Figs. <a href="#plate1">4</a>, <a href="#plate1">7</a>, <a href="#plate2">22</a>, vb, pz, nz.)</p> - -<p>The cells composing the retina form a single layer in the shape -of a hollow cup, into which cup the lens with its capsule fits. (<a href="#plate1">Fig. 7</a>.) -This single layer of cells takes in the thickness of the vitreous zone, -the pigmented zone, and the nuclear zone. Indeed, the distinctions -vitreous zone (vitreous body), pigmented zone, and nuclear zone -characterize three topographical regions of the retinal cells.</p> - -<p>That the retina is made up of three kinds of cells is most -readily demonstrated in transverse sections through the vitreous -body. <a href="#plate1">Fig. 1</a> is such a section, taken quite near the pigmented -zone (at about the level x, <a href="#plate1">Fig. 4</a>). Three different kinds of areas -are readily made out in such a section. The more numerous areas<span class="pagenum"><a name="Page_46" id="Page_46">[46]</a></span> -(pr) are transverse sections of the distal prisms of the prism cells, -the less numerous and lighter areas (pyr) are transverse sections -of the pyramids of the pyramid cells, and the large oval heavily -pigmented areas (lp) are the transverse sections of the long pigment -cells. The dots within the two first named areas represent fine fibers -in the axes of the prism and pyramid cells, to be described below. -The presence of three kinds of cells can again be readily seen in -such Figs. as <a href="#plate1">4 and 7</a>, in which the elements of the retina are cut -parallel to their long axis. (<a href="#plate2">Fig. 22</a>.) Again, a transverse section -through the most distal part of the pigmented zone of a slightly -pigmented retina (<a href="#plate1">Fig. 2</a>) also shows us the presence of three kinds -of elements. The larger and more heavily pigmented areas (lp) are -the long pigment cells; the smaller, lighter areas (pyrc) with a -central dot are the pyramid cells, and the more numerous dots, with -no definite polygonal areas outlined about them (prc), belong to the -prism cells. Thus, I believe, we have conclusive evidence of the -existence of three kinds of cells in the retina of the distal complex -eye.</p> - -<p>(a) The prism cells are the more numerous, and, as the name -implies, end distally in a vitreous polygonal prism (Figs. <a href="#plate1">4</a>, <a href="#plate1">7</a>, <a href="#plate2">22</a>, pr). -The prismatic structure of the vitreous body is also shown in <a href="#plate1">Figs. -10 and 11</a>, which are drawn from a macerated preparation of Conant’s. -(See the descriptions of these figures.)</p> - -<p>In <a href="#plate1">Figs. 4 and 7</a> the prism cells correspond to the cells with -the darker nuclei (npr); in <a href="#plate1">Fig. 2</a> they are represented by the dots -without defined polygonal areas about them (prc), and in <a href="#plate1">Fig. 1</a> by -the most numerous areas (pr). These cells, then, consist of a centrad -portion with nucleus, a pigmented portion with granules of a dark-brown -pigment, distal from the nucleus, and a distal vitreous prism -which extends to the capsule of the lens.</p> - -<p>In the axis of each prism is a fine darkly-staining fibril extending -the entire length of the prism. I found no good evidence that this -fiber extends into the capsule. Centrad this fiber is continued -through the pigmented part of its cell and approaches to or near -the nucleus (<a href="#plate1">Fig. 2</a>, dots without defined polygonal areas; <a href="#plate1">Fig. 7</a>, -part of retina left unpigmented). In some instances I could trace -this fiber quite to the nucleus, while in others it ended before reaching -the nucleus or a little to one side of it. I am inclined to believe, -however, that it extends past the nucleus and is continued as a nerve<span class="pagenum"><a name="Page_47" id="Page_47">[47]</a></span> -fiber. I believe this to be so because the fiber is evidently sensory, -and <i>a priori</i> we should expect it to be so continued. Further, I -find decided evidence in sections of the simple eyes to show that the -fibers there extend past the nucleus into the subretinal tissue where -I could not trace them farther. (<a href="#plate2">Fig. 16</a>.) Again, that the flagella -of the epithelial cells of the club are also continued into the cells, -in some instances could be traced past the nuclei (Figs. <a href="#plate2">12</a> and <a href="#plate3">26</a>), -and the fact, too, that the retinal cups of the eyes represent -invaginated epithelium (the axial fibers of the prisms are hence -cilia?)—all this leads me to believe that the axial fibers of the prism-cells -extend centrad past the nuclei through their cells and are -continued as nerve-fibers. (See below under pyramid-cells and under -epithelium). Immediately upon entering the pigmented part of its -cell the axial fiber of a prism-cell has a dumbbell-shaped enlargement -which lies quite at the distal edge of the pigmented part -of the cell (<a href="#plate1">Fig. 7</a>, unpigmented part of figure). This, of course, can -be seen only in unpigmented retinas. This dumbbell-shaped body, -(Basalkörperchen of Apathy), which name I give it, since it evidently -is homologous to the basal bodies described by others for the cilia of -epithelia, can be most beautifully seen as two minute spheres lying -close together and in line with the nucleus. These two little spheres -of the basal bodies put to the test the highest powers of the -microscope; but, when, after a prolonged and careful study, one -satisfies himself of their existence and exact shape, the very difficulty -with which they are resolved adds a zest to be appreciated. The -length of a basal body is about one-fifth to one-fourth that of the -nuclei of the prism-cells.</p> - -<p>The structure of the nuclei of the prism-cells is that of a dense -network (<a href="#plate1">Figs. 4, 7</a>, npr) which stains dark with hæmatoxylin. A -nucleolus can often be seen in these nuclei. In some few series, -again, these nuclei did not show a network-like structure, but the -chromatin was arranged in masses (<a href="#plate1">Fig. 5</a>, npr). These nuclei can -usually be distinguished from those of the other cells of the retina -by their denser, darker-staining network (<a href="#plate1">Figs. 4, 7</a>, npr), or as -shown in <a href="#plate1">Fig. 5</a> (npr). Their denser structure and staining capacity -are a distinguishing characteristic of the nuclei of the prism-cells. -I must add, however, that not in every series is this apparent.</p> - -<p>That portion of a prism-cell that contains the nucleus rarely -contains any pigment; and when pigment is present, I believe that<span class="pagenum"><a name="Page_48" id="Page_48">[48]</a></span> -it has been dissolved in from the pigmented zone. The nucleus, -again, lies a little centrad from the pigmented part of its cell, so that -an unpigmented zone is seen in the retina between the pigmented -zone and the row of nuclei (Figs. <a href="#plate1">4</a>, <a href="#plate1">7</a>, <a href="#plate2">22</a>).</p> - -<p>Centrad the prism-cells are continued as a single process (<a href="#plate1">Figs. -6, b, c, d, and 8a, b, c, d</a>). In some sections I thought I could trace -these processes to the basement membrane, but I could not satisfy -myself that such appearances were not due to artificial splitting in -the tissue. Schewiakoff makes a similar remark about his supporting -cells, which cells I believe are the same as my long pigment cells, -but these do not extend to the supporting lamella.</p> - -<p>At the margin of the retina the cells do not develop prisms but -remain pigmented and form an iris (<a href="#plate1">Fig. 7</a>), which was so named by -Claus and also described by Schewiakoff. These cells also assume a -somewhat different shape (<a href="#plate1">Fig. 6a</a>). This cell (<a href="#plate1">Fig. 6a</a>) is seen from -its broader side with which it is applied to the capsule or the lens. -Schewiakoff figures similar cells. That the cells of the iris are prism -cells without the prisms does not necessarily follow. They simply -represent cells of the retinal cup that have become differentiated to -serve as an iris.</p> - -<p>As to the exact origin of the prisms, and pyramids (to be -described below), it is difficult to say anything definite. If the -so-called basal bodies of the axial fibers are really homologous with -the basal bodies of flagella, then it would seem that they (the prisms -and pyramids) are secretions comparable to cuticular secretions.</p> - -<p>(b) The pyramid-cells, like the prism-cells, are differentiated -into three regions: a distal vitreous pyramid, a pigmented part, and -a centrad part with nucleus. The pyramids are seen in transverse -section in <a href="#plate1">Fig. 1</a> (pyr) and in longitudinal section in <a href="#plate1">Figs. 4 and -7</a> (pyr).<a name="FNanchor_5" id="FNanchor_5"></a><a href="#Footnote_5" class="fnanchor">[e]</a></p> - -<p>Each pyramid extends between the bases of the prism-cells -about one-third to one-half the depth of the vitreous body (Figs. -<a href="#plate1">4</a>, <a href="#plate1">7</a>, <a href="#plate2">12</a> (pyr)). The pyramids are also a shade lighter than the prisms,<span class="pagenum"><a name="Page_49" id="Page_49">[49]</a></span> -which fact is characteristic. In the axis of each pyramid is a -darkly-staining fiber quite like the one described for the prism-cells -(Figs. <a href="#plate1">1</a>, <a href="#plate1">4</a>, <a href="#plate1">7</a>, <a href="#plate2">22</a>). That this fiber extends distally beyond the -limits of the pyramids I could not determine, but I do not think -that it does. Centrad this fiber extends into the pigmented portion -of its cell quite to or near the nucleus as was described for the -fibers of the prism-cells (Figs. <a href="#plate1">7</a>, <a href="#plate2">22</a>). Whether or not these fibers -extend past the nucleus and become continued as nerve fibers, the -same course of reasoning holds as was given for the fibers of the -prism-cells. Each of these fibers possesses a basal body just on its -entrance into the pigmented part of the cell (<a href="#plate1">Fig. 7</a>), but I could -not determine that it was dumbbell-shape. In form it represents -an enlargement of the fiber itself, which gradually tapers again to -its normal size. The continuations of these fibers within the pigmented -parts of the pyramid-cells, as also the basal bodies, could -only be demonstrated in unpigmented series.</p> - -<p>Patten<span class="fnanchor"><a href="#book5a">[5]</a></span> describes axial fibers extending centrad through the rods -(vitreous portions) of retinal cells (“retinophora”) into the region -of the nucleus and past the nucleus (arthropods and molluscs). My -retinal cells (prism and pyramid cells) evidently correspond to Patten’s -retinophora, but I find no evidence that one of my retinal cells -represents more than a single cell, while Patten gives evidence that -his retinophora are made up of two cells closely applied to each other -as twin cells. If this were also true for the retinal cells that I have -described, I believe my macerated preparations would have shown -it. Schreiner<span class="fnanchor"><a href="#book12b">[12b]</a></span> and Hesse<span class="fnanchor"><a href="#book13">[13]</a></span> also figure and describe axial fibers for -the rods of the visual cells in polychætous annelids, and Schreiner<span class="fnanchor"><a href="#book12a">[12a]</a></span> -also for molluscs. Neither of these observers finds the fibers to extend -distally beyond the rods nor centrad toward the nucleus as Patten -and myself show. Neither Schreiner nor Hesse figures these cells as -twin cells as Patten does, so that to my knowing Patten stands -alone in this respect. Andrews<span class="fnanchor"><a href="#book14">[14]</a></span> describes and figures rods for the -visual cells of polychæte annelids but no axial fibers. He was the -first to describe these rods in annelids.</p> - -<p>The pigmented zone of the pyramid cells, in heavily pigmented -series, is filled throughout with dark-brown pigment granules, and is -quite like that of the prism cells (<a href="#plate1">Figs. 4, 7</a>). In transverse sections, -however, through the most distal part of the pigmented zone, of -unpigmented series (<a href="#plate1">Fig. 2</a>), lighter areas with central dots could<span class="pagenum"><a name="Page_50" id="Page_50">[50]</a></span> -occasionally be demonstrated, which areas are the pyramid cells. In -<a href="#plate1">Fig. 2</a>, the more definite polygonal outline as well as the lighter shade -of these areas was a distinguishing feature. The difference in shade -was not wholly due to a difference in pigmentation but to a -structural difference.</p> - -<p>The nuclei of these cells are usually a little larger than those of -the prism cells and are filled with a finer and less dense network -(<a href="#plate1">Figs. 4 and 7</a>, npyr), in consequence of which they present a lighter -appearance in sections when examined with a high power. It will be -seen in the figures (<a href="#plate1">4, 7</a>) with what regularity these lighter nuclei -lie opposite the pyramids. Some few exceptions occur. These are -probably due to the fact that a nucleus or pyramid was not differentiated -by the technique. If this opposition between the pyramids and -the lighter nuclei were all, I believe it would be sufficient evidence -for associating these lighter nuclei with the pyramid cells.<a name="FNanchor_6" id="FNanchor_6"></a><a href="#Footnote_6" class="fnanchor">[f]</a></p> - -<p>(c) The <em>long pigment cells</em> are about as numerous as the pyramid -cells. In these cells, as in the prism and pyramid cells, three regions -can be distinguished: the region of the nucleus, a pigmented region -(the distal half of which extends between elements of the vitreous -body), and a distal rod-like portion, or fiber, which is continued -between the prisms into the capsule of the lens (<a href="#plate1">Figs. 4, 7, 9</a>). The -pigmented portion is about twice the length of that described for the -other cells, and also often of greater diameter, so that in transverse -sections (<a href="#plate1">Figs. 1, 2, 3</a>) these cell-areas are larger than those of the -other cells. As nearly as I could determine, these cells are pigmented -just like the other retinal cells described. In quite unpigmented series, -however, they often contain more pigment than the other cells do<span class="pagenum"><a name="Page_51" id="Page_51">[51]</a></span> -(<a href="#plate1">Fig. 2</a>). Distally, the pigmented part becomes narrowed to a strong -pigmentless fiber (<a href="#plate1">Figs. 3, 4, 7</a>). This fiber stains quite dark with -iron-hæmatoxylin and appears homogeneous. It passes between the -prisms into the capsule, where it usually bends in a direction toward -the margin of the capsule (<a href="#plate1">Fig. 7</a>) and passes diagonally across this -to the lens. In sections, a space is often seen about these fibers in the -vitreous body, which I regard as a shrinkage space (<a href="#plate1">Figs. 3, 4</a>), since -it is not evident in all series (<a href="#plate1">Fig. 1</a>). In <a href="#plate1">Fig. 7</a>, I have assumed that -these spaces are due to shrinkage and have not indicated them. Also, -in this same figure I have assumed that the spiral appearance of the -fibers (<a href="#plate1">Fig. 4</a>) is due to a shortening of the prisms during fixation, -and have drawn them straight. At the lens these fibers seem to -end. In a few instances they were seen to branch upon reaching -the capsule (<a href="#plate1">Fig. 4</a>). In <a href="#plate1">Fig. 9</a>, also, which shows some of these cells -from a macerated preparation by Conant, the rods show evidence of -branching at their distal terminations. In the same preparation I -thought I could see that a fiber became expanded into a membrane -spreading over one of the lens-cells. I could not satisfy myself, -however, that this was the actual condition of things. Judging from -<a href="#plate1">Fig. 9</a>, one might conclude that all the fibers are branched distally; -yet, if such were the case I should have seen more of it in sections, -but branching as seen in <a href="#plate1">Fig. 4</a> is the exception. Hence, if all these -fibers do branch, I am inclined to believe that it must be among the -bases of the lens-cells. Or, if the fibers do expand into membranes to -cover the lens-cells (I could not explain purpose), the evidence in -<a href="#plate1">Fig. 9</a> may be nothing more than fragments of this membrane left -attached to the ends of the fibers. As is seen in <a href="#plate1">Fig. 7</a>, most of these -rods end opposite the cells of the lens, and not usually between two -adjacent cells as Schewiakoff has described for Charybdea marsupialis. -The nuclei of these cells are like the nuclei of the pyramid cells (<a href="#plate1">Figs. -4, 5, 7, 9</a>) and often have a nucleolus.<a name="FNanchor_7" id="FNanchor_7"></a><a href="#Footnote_7" class="fnanchor">[g]</a> Centrad these cells are -continued into a number of processes as is seen in <a href="#plate1">Figs. 5, 7 and 9</a>. -How far the several centrad processes extend and where they end I -cannot say; but, as seen in <a href="#plate1">Fig. 5</a>, they soon taper to a thin end -which I suppose may be continuous with a nerve fiber. I believe -Schewiakoff was mistaken when he stated that these cells extend to -the basement membrane.</p> - -<p><span class="pagenum"><a name="Page_52" id="Page_52">[52]</a></span></p> - -<p>I have found no evidence in these cells of the existence of an -axial fiber such as I have described for the prism and pyramid cells. -I find no definite arrangement of the nuclei of the retina into definite -layers, but the nuclei of the three kinds of cells lie quite mixed, -sometimes one kind lying deeper than the other as can be seen in -the figures. Again, they may lie quite at the same level. (This -point will be referred to later.)</p> - -<p>It is these long pigment cells that I believe retract their -pigmented part from between the prisms and pyramids when the -medusæ are placed in the dark, protruding with their pigment -when placed in the light. <a href="#plate1">Fig. 5</a> is a section from a slightly -pigmented retina killed in the dark. The parts of the cells projecting -beyond the pigmented zone, and which would lie between -the prisms and pyramids (here not shown) of the vitreous body are -seen to be narrower than in sections from retinas killed in the light -(<a href="#plate1">Figs. 1, 3, 4, 7</a>) and the cells themselves appear in a condition of -retraction as is shown by their large centrad portions with the nuclei, -which latter, also, here lie at quite a lower level than the other nuclei. -(The pyramid cells were not shown in this series.) I occasionally -found appearances like <a href="#plate1">Fig. 5</a> in retinas killed in the dark (indeed, -in some the pigmented portions in the vitreous body were much -thinner and more retracted than in <a href="#plate1">Fig. 5</a>). Yet this appearance -was not of sufficiently general occurrence to leave no doubt as to -its significance. As positive evidence, however, I cannot give it any -other interpretation than the one given—that the cells retract -themselves with their pigment when in the dark. Again, it must -be added that the nuclei of these cells may occasionally lie quite -deep even in retinas killed in the light. Indeed, like structures in -different retinas may vary considerably in size and shape. None -of my darkness retinas, however, showed such a large proportion of -the pigmented parts of the long pigment cells projected between -the prisms and pyramids as did the light retinas. I examined -and tabulated all my series with respect to the extent the long -pigment cells were projected into the vitreous body, and I found -that those which showed these cells with their pigment least -projected between the prisms and pyramids to be those that had -been killed in the dark. I thus feel satisfied that the pigmented -parts of these cells become in part or quite completely retracted from -between the prisms and pyramids of the vitreous body when in the<span class="pagenum"><a name="Page_53" id="Page_53">[53]</a></span> -dark, but just how this is accomplished—whether the whole cell with -its nucleus takes up a deeper position, the cell substance at the same -time collecting in the region about the nucleus, as shown in <a href="#plate1">Fig. 5</a> -and the diagram (<a href="#plate2">Fig. 22</a>), I cannot with certainty state. It would -seem, too, as though the pigment became less in the cells exposed to -darkness, for I rarely, even in the most retracted heavily pigmented -series, saw the pigment to extend farther towards the nucleus than -commonly. The time of keeping in the dark, prior to fixing, varied -from three-fourths of an hour to one and one-half hours. I could -not bring the amount of retraction into relation with the time of -exposure, except that in general the retinas longest exposed showed -the greater amount of retraction.</p> - -<p>(d) The tissue underlying the retina is described by former -observers (Claus, Schewiakoff, Conant) as composed of nerve-fibers -and ganglion cells. I cannot give it any other interpretation, but I -must add that the supposed ganglion cells are seen only as nuclei, -no cell bodies ever being demonstrable in any of my sections. Conant -also recognized no cell bodies. Occasionally, as in <a href="#plate1">Fig. 7</a>, long fibers -could be traced for some distance in this subretinal tissue, in some -instances quite to or from a visual cell. Pigment was not regularly -observed in this tissue, as Schewiakoff describes, and when present I -believe it has been dissolved in from the pigmented zone.</p> - -<p>(e) Schewiakoff describes the retina (my pigmented and nuclear -regions) as composed of spindle-shaped visual cells (my pyramid -cells?) alternating with pigmented supporting cells (long pigment -cells), with the nuclei of the former lying more centrad than those of -the latter. The visual cells are pigmented only at their periphery, or -surface, leaving an unpigmented axis, while the supporting cells have -pigment throughout their whole substance within the pigmented -zone. Distally, the visual cells have hyaline rods, or fibers, which -extend into spaces in the vitreous body, and pass through this and -the capsule to the lens. The vitreous body is described as homogeneous, -except the spaces for the visual rods, and a secretion from the -retinal cells.</p> - -<p>It will thus be seen that my results are quite different from -those just described. I find the vitreous body to be composed of -prisms and pyramids with axial fibers, while the long pigment -cells (supporting cells of Schewiakoff) are continued into the -vitreous body, and becoming narrowed into a non-pigmented fiber,<span class="pagenum"><a name="Page_54" id="Page_54">[54]</a></span> -extend to the lens as described. The prisms and pyramids are, -further, the distal continuations of cells whose pigmented and -nuclear parts lie in the so-called retina, but which, together with the -vitreous body, I have named the retina proper. Conant has so summarily -disposed of Schewiakoff’s distinction between retinal cells based -on pigmentation and location of nuclei, that I need not say more. -Schewiakoff’s Fig. 18 corresponds to my <a href="#plate1">Fig. 1</a>. In this figure he -shows the vitreous body as homogeneous with pigmented areas -(my long pigment cells) and with spaces with his visual rods. It is -quite evident that his spaces with the visual rods correspond to -my lighter areas with central dots; <i>i. e.</i> my pyramids of the -vitreous body are the same as the spaces shown in his Fig. 18. -It is quite evident that Schewiakoff mistook the lighter areas for -spaces. That they are not spaces can readily be seen by comparing -them with real spaces. It is, of course, possible, too, that the reagents -had dissolved the pyramids, leaving only the axial fibers with a little -pyramid substance about them, and that this is what Schewiakoff -saw. I often found small circular spaces in the centers of the -pyramid areas, as also in the prism areas (<a href="#plate1">Fig. 3</a>), which might be -taken for hyaline visual rods, fibers, in transverse section, but in -such spaces I could usually see a small dot to one side of the space -that I take to be the rod (fiber) proper. <a href="#plate2">Fig. 14</a> also shows such -small circular spaces that have very much the semblance of hyaline -rods. This figure is a transverse section of the vitreous body of the -proximal complex eye, in which no long pigment cells or pyramid -cells are present, but it serves well to illustrate the point. The above -explanation also accounts for the large size of the visual rods (fibers) -in Schewiakoff’s figures. That the fibers of the pyramid cells (visual -rods of Schewiakoff) do not extend to the lens is quite evident in my -<a href="#plate1">Figs. 4 and 7</a>.</p> - -<p>Again, since the long pigment cells are often not seen to terminate -in a fiber, but a part of the fiber can often be seen in the -distal part of the vitreous body and in the capsule, it will be quite -readily seen how Schewiakoff should associate his visual rods, or -fibers, with these distal parts of the fibers of the long pigment cells -and suppose his visual rods to extend to the lens.</p> - -<p>Again, since the long pigment cells sometimes cannot be seen to -terminate distally in a fiber, while the vitreous body at the same -time may be broken away from the pigmented zone (<a href="#plate1">Fig. 4</a>), it is<span class="pagenum"><a name="Page_55" id="Page_55">[55]</a></span> -quite evident how Schewiakoff should have interpreted the parts of -the long pigment cells in the vitreous body as conical pigmented caps -placed opposite his supporting cells (long pigment cells).</p> - -<p>Finally, since Schewiakoff had only twelve marginal bodies to -study, and since this tissue is difficult to preserve properly, I do not -believe that I am doing Schewiakoff any injustice by explaining away -his results as I have done. This fact remains, that Conant and -myself agree in all points in which we differ from Schewiakoff.</p> - -<p>To Conant belongs the credit of having first demonstrated the -prismatic structure of the vitreous body, and he also regarded the -prisms as a part of the retinal cells. H. V. Wilson<span class="fnanchor">[<a href="#book15">15</a>, <a href="#book8b">8b</a>]</span> suggested, -however, some years prior to Conant, that the vitreous body might -be of a prismatic structure. Conant had evidence also of both the -prism and pyramid fibers, as is well shown in his figures of transverse -sections but he found his evidence too meager to make any -very definite statements. Indeed, Conant concludes that there are -three kinds of fibers in the vitreous body and complains of finding -but two kinds of cells in the so-called retina (pigmented and nuclear -zones) to which to refer them. He saw the pyramids with their -axial fibers as lighter areas in transverse sections of the vitreous -body (his Figs. 64 and 68, and my <a href="#plate1">Figs. 1, 4 and 7</a>), but suggests -that they may be the same as the long pigment cells, the cells -having only to project themselves or their pigment in order to -become long pigment cells. This suggested to him to preserve -material both in the light and in the dark. I do not think Conant’s -supposition to be a fact, for I find the pyramids in specimens -preserved in the light as well as in the dark. It is, of course, -possible that the pyramid cells are in a stage of structural transition -to the long pigment cells, for, besides their pigmentation, they also -have like nuclei. Furthermore, I held for a long time with Conant -that there may be only two kinds of cells in the retina, but I soon -found the pyramids so definitely shown as to leave no doubt but -that they represented a third kind of cell. For me it remained to -first definitely see all the fibers in the vitreous body as also the -pyramids in sagittal sections.</p> - -<p>Conant describes the long pigment cells with their fibers extending -between the prisms of the vitreous body quite as I have described, -and in this my work is only confirmatory of his. Conant does not, -however, describe the several centrad processes of these cells, nor is<span class="pagenum"><a name="Page_56" id="Page_56">[56]</a></span> -he clear that their distad processes extend to the lens, though he -speaks of fibers within the capsule.</p> - -<p>(f) What, now, is the function of these three varieties of cells -of the retina? Schewiakoff regards his visual cells (pyramid cells), -as the name implies, as having a visual function. That they have -such it seems reasonable to suppose, since they have an axial fiber -in their pyramids. If the pyramid cells are visual cells, it appears -that the prism cells also are such. Indeed, since these are the only -ones present in the proximal eye and the more numerous ones in the -distal eye, and like the pyramid cells have an axial fiber in their -prisms, it seems that they are the visual cells <i lang="fr">par excellence</i> of the -Cubomedusan eye. Also, the analogy between the prisms and -pyramids on the one hand, and the rods and cones of the vertebrate -eye on the other hand, does not seem to be so far fetched. It may -be of interest, here, to briefly consider Patten’s theory of color -vision.<span class="fnanchor"><a href="#book5b">[5b]</a></span></p> - -<p>The gist of Patten’s theory is this: In the eyes of certain -molluscs and arthropods, in the parts of the retinal cells corresponding -to my prisms and pyramids, he not only finds an axial -fiber (or fibers) but finer fibrils that extend at right angles from -these axial fibers to the surface of the rods (I shall here, for -convenience, call the prisms, pyramids, etc., rods) where they probably -become continuous with other fibrils in the surface of the rods. -These fibrils from the axial fibers are arranged in superimposed -planes, and if I understand rightly, an axial fiber with its radiating -fibrils may be compared to the axial wire with its radiating bristles -of a brush used for cleaning bottles, provided the bristles of such -a brush be arranged in superimposed planes. The lateral arrangement -of the fibrils will, of course, be modified according whether -a rod is circular, hexagonal, square, etc., in transverse section. It -will also be remembered (<a href="#Page_49">p. 49</a>) that Patten describes the retinal -cells studied by him as composed of twin cells, and he gives the -name <em>retinophora</em> to a pair. The system of fibers and fibrils in the -rods he names a <em>retinidium</em>. Centrad the axial fibers are continued -past the nucleus as a nerve fiber. The fibrils extending laterally in -superimposed planes from the axial fiber of a rod, Patten supposes -to be the ones stimulated by the incoming rays of light, the -retinophora being so arranged that the light rays entering them are -parallel to the axial fibers or perpendicular to the lateral fibrils of the<span class="pagenum"><a name="Page_57" id="Page_57">[57]</a></span> -retinidium. Again, since the rods are usually the shape of truncated -pyramids or cones the lateral fibrils, which are perpendicular to the -axial fibers, are of different lengths accordingly as they are situated -at the larger or smaller end of a rod. Patten assumes similar fibrils -to exist in the rods and cones (particularly the cones) of the vertebrate -eye, and he thus makes a general application of his theory. -He supports himself in this rather sweeping generalization by the -claim to have demonstrated the twin-cell nature of the cones in -amphibia and fishes.</p> - -<p>For illustration, Patten supposes that if red light only were -admitted to the retinophora this would stimulate the fibrils near the -broader end of the cone (but that all the fibrils of the retinidium -would be stimulated a little) and that we would thus have the -sensation of red light. Likewise, if violet light only were admitted, -the fibrils at the narrower end of the cone would be stimulated, and -we should have violet light. Similarly, if light including all the -different wave lengths of the spectrum were admitted, all the lateral -fibrils would be stimulated and the sensation of white light produced. -The method of stimulation need not be that of a vibration of the -fibrils.</p> - -<p>Certain grave objections may be raised against such a theory, -the most serious, perhaps, being the fact that no such fibrils as -Patten has described have as yet been demonstrated for the eyes of -those animals that we know have color vision. Yet, as a whole, the -objections are perhaps no more serious than any that can be brought -against other theories of color vision. What Patten’s theory does do,—it -gives us a definite mechanical basis to work from, and if these -fibrils should be demonstrated for the rods and cones of vertebrates, -physiologists would then have a mechanical basis for color vision -quite as they now have for hearing. As Patten says, the problem -is primarily a mechanical one. However, the theory cannot well -pass for more than a suggestion, a stimulus for future work, and in -this lies its present value.</p> - -<p>It is quite evident that my results for the retinal cells of -Charybdea are, if any thing, a support to Patten’s theory. While I -have not been able to demonstrate the fibrils that are the essential -to Patten’s theory, yet I have demonstrated the axial fibers of the -rods, and if these fibers should be continued as a nerve fiber to some -central ganglion (as I believe is reasonable to suppose, see <a href="#Page_47">p. 47</a>), I<span class="pagenum"><a name="Page_58" id="Page_58">[58]</a></span> -do not see how we can avoid the conclusion that these axial fibers -of the prism and pyramid cells are somehow concerned in vision. -In Patten’s theory these fibers would represent a conducting element, -the real sensory element (fibrils perpendicular to these axial fibers) -not having been demonstrated by me.</p> - -<p>I have recently read in a short review of Patten’s theory<span class="fnanchor"><a href="#book9">[9]</a></span> that -the evidence we at present have points to the tips of the cones -(vertebrate eye) as being the seat of the sensation of red. This would -be exactly the converse of what Patten’s theory supposes. Whether -or not this objection is a real one, future investigation only can -determine.</p> - -<p>Hesse<span class="fnanchor"><a href="#book13">[13]</a></span> regards the axial fibers that he describes for the rods in -worms as the primitive fibers of Apathy. In this I agree with him, -regarding the axial fibers I have described as “Primitivfibrillen.” -Further, I believe, if I understand Apathy rightly, that the fibrils -described by Patten as extending laterally from the axial fibers -correspond to Apathy’s “Elementarfibrillen.”</p> - -<p>It is the long pigment cells that are the puzzling element. Since -there can be little doubt but that these cells can project and retract -their pigmented parts (as already described), it would seem that a -part of their function is to check the diffusion of light in the vitreous -body when exposed to strong light. This function would be quite -analogous to that of the pigmented cells of the vertebrate retina, -which in light become projected between the rods and cones. Similar -observations have also been made on the compound eyes of arthropods -by Herrick<span class="fnanchor"><a href="#book10">[10]</a></span> and by Parker<span class="fnanchor"><a href="#book7">[7]</a></span>, who find that the distal retinula cells of -Palæmonites project themselves distad in the dark, thus surrounding -the vitreous cones with a cylinder of pigment, while (Parker) the -pigment of the proximal retinula cells migrates centrad and the -accessory cells move distad; in light the reverse takes place. Other -observations of this kind are not wanting for crustacea, insects and -arachnids. To my knowledge, the pigment changes that I have -described are the first of their kind for medusæ.</p> - -<p>I suggested while describing the capsule, that the lens might be -adjustable. That the fibers of the long pigment cells extend to the -lens is my principal reason for this. May these cells not represent -ganglion cells and their distad fibers nerve fibers? That they are not -sensory (<i>i. e.</i> are stimulated by light waves) seems to be suggested by -their not having any axial fiber and in having several centrad processes.<span class="pagenum"><a name="Page_59" id="Page_59">[59]</a></span> -These facts suggest that they are not sensory but the center -of a reflex mechanism.<a name="FNanchor_8" id="FNanchor_8"></a><a href="#Footnote_8" class="fnanchor">[h]</a> When the sensory cells proper are stimulated, -the impulses are conducted centrad into some nerve center (it may -be the nerve tissue underlying the retina, or other nerve centers such -as the two groups of ganglion cells in the upper part of the club, or -the radial ganglia) from which center, again, impulses return over -fibers leading to the long pigment cells causing them to project their -pigment, and conducting the impulse to the lens, to produce a change -in its adjustment. Since these cells are not so numerous as the -prism and pyramid cells taken together, but in turn have a number -of processes continued centrad (the sum of which processes approximates -the number of sensory cells, prism and pyramid cells) it -appears that these cells are admirably adapted to function in just -such a mechanism as I have described,—each long pigment cell -serving a number of its immediate neighbors.</p> - -<p>Further, we may conceive each of the centrad processes of the -long pigment cells as receiving a fiber from one of the sensory -cells directly as well as indirectly, as just described. While I -have been able to demonstrate only a single centrad process for the -sensory cells (prism and pyramid cells), yet this does not exclude the -possibility of a nerve fibril passing out from such a centrad process -to one of the processes of the long pigment cells, and it seems -possible that this constitutes the reflex mechanism. That nerve fibrils -ramify in ganglion and sensory cells, and may even leave these cells -to join those of other cells, has been well demonstrated by Apathy,<span class="fnanchor"><a href="#book6">[6]</a></span> -so that my finding only a single process of the visual cells leading -centrad without giving off lateral fibers cannot be a serious objection. -Again, fine nerve fibers coming off from the main centrad process of -sensory cells in medusæ have been figured by other observers, among -whom I mention the Hertwigs. Careful macerations at the seashore -would probably demonstrate them for Charybdea.</p> - -<p>Hesse thinks that the eyes of the Alciopidæ are adjustable. He<span class="pagenum"><a name="Page_60" id="Page_60">[60]</a></span> -describes what he supposes to be muscle fibers just exterior (distal) -to the lens, and believes that a contraction of these fibers would -have the effect of forcing the lens nearer the retina, or <i>vice -versa</i>. His supposition, like mine, needs experimental verification. -Hitherto the only instance known of accommodation in the eyes of -invertebrates was that described by Beer<span class="fnanchor"><a href="#book17">[17]</a></span> for Cephalopods.</p> - -<p class="section"><i>The Proximal Complex Eye.</i>—With four exceptions, the description -and discussion given for the distal complex eye also holds good for -the proximal complex eye (<a href="#plate2">Fig. 13</a>). The four exceptions are: the -absence of a capsule to the lens; the absence of the long pigment -cells; the absence of the pyramid cells; and the different relative -position of the lens and retina. This eye, then, has a cornea -continuous with the epithelium of the sensory club, a lens, in -structure and probable origin quite like that described for the distal -complex eye, and a retina of prism cells with axial fibers for the -prisms. Since Conant<span class="fnanchor"><a href="#book8b">[8b]</a></span> has described this eye quite fully, and -discussed Schewiakoff’s conclusions at length, I shall be brief. -Suffice it to say, that Schewiakoff describes two kinds of cells -(supporting cells and spindle-shaped visual cells) for the retina of -this eye just as he described for the distal complex eye. The -vitreous body he likewise describes as being homogeneous and with -spaces for the visual rods (fibers) of the visual cells. It is evident -that Schewiakoff has interpreted the structure of this eye from -analogy with his results on the distal complex eye. Claus likewise -has described two kinds of cells for the retina, and the vitreous -body as homogeneous. Conant and myself find only one kind of -cells in the retina of this eye. The pigmentation that Schewiakoff -describes for the vitreous body I believe to have been dissolved in -from the pigmented zone of the retina, for I find no regular -pigmentation in the vitreous body. Haake’s observation, previously -noted (<a href="#Page_42">p. 42</a>), applies also to the proximal complex eye.</p> - -<p>Conant’s evidence for the axial fibers of the prisms was clearly -insufficient, so that he did not in this respect complete his Fig. 69. -I republish this figure with the prism fibers drawn (<a href="#plate2">Fig. 13</a>).</p> - -<p>Since the long pigment cells are absent my reasons for supposing -the lens of this eye to be adjustable vanish.</p> - -<p>Finally, a word on the origin of the lens and the relative -position of the lens and retina. The lens and retina in this eye<span class="pagenum"><a name="Page_61" id="Page_61">[61]</a></span> -are evidently not developed from an outer and an inner half, -respectively, of the invaginated and pinched-off lens-retina sphere -(as is true for the distal complex eye) but from proximal and distal -halves respectively. It is also quite easy to understand the -connection of the lens in this eye with the supporting membrane. -Since the cells of the ectoderm of the club can in many instances -be seen to extend to the basement membrane, or supporting lamella, -the cells of the lens, which arise from the ectoderm, simply remain -in connection with the basement membrane, this becoming thickened -to form a support for the lens. That the lens of the distal complex -eye has lost its connection with the basement membrane is evidently -due to the fact that the lens is formed from the outer half of the -lens-retina sphere. The cells of the lens are by this so far separated -from the basement membrane as to lose their connection with it. -Schewiakoff also notes the fact that the lens and retina of the -proximal complex eye are developed from proximal and distal halves -of the lens-retina sphere. He further supposes that the portion of -the basement membrane that acts as a support to the lens takes the -place of the capsule in the distal complex eye. This latter supposition -I do not think probable, since the supporting lamella does not form -a distinct covering to the lens on its retinal side.</p> - -<p class="section"><i>The Simple Eyes.</i>—Since the shape and position of these eyes -have already been described (Claus, Schewiakoff, Conant), I shall not -tarry long in this respect. Speaking generally, these eyes are flask-shaped -(<a href="#plate2">Fig. 12</a>), the proximal pair quite so, while the distal pair are -drawn out in the transverse diameter of the club. These eyes are -invaginations of the surface epithelium and the shape of the cells -lining these invaginations is quite like that of the epithelial cells, -except that their distal portions (bordering the lumen of the invagination) -are heavily pigmented. The proximal walls (<a href="#plate2">Fig. 12</a>, left side) -of the distal pair are heavier pigmented than the distal walls and the -proximal pair of eyes. Schewiakoff calls attention to this point. -The pigmentation is, furthermore, not only heavier, but the pigmented -portion of each cell is much longer in the proximal walls of the -distal eyes (indeed, the cells are longer) than in the distal walls. -The significance of this I do not understand. Indeed, I am inclined -to believe that in life all these eyes are pigmented quite alike and -that it is the reagents used that alter or dissolve the pigment in<span class="pagenum"><a name="Page_62" id="Page_62">[62]</a></span> -certain places. Yet, the fact that the cells of the proximal walls -of the distal eyes have their pigmented portions nearly double the -usual length, shows some deeper significance.</p> - -<p>I also note here the small secondary, non-pigmented invagination -into the tissue of the clubs from each of the distal simple eyes. -Schewiakoff describes this invagination, and it extends in a proximal -and dorsal direction (dorsal-side of club opposite complex eye) from -the dorsal sides of the distal simple eyes. The cells of these -invaginations are not pigmented, but quite like the other pigmented -cells in shape, and like these with distal flagellate fibers. I do not -see the necessity of assuming, however, that these secondary invaginations -are the real sensitive parts of these eyes, while the pigmented -parts serve as an iris, as Schewiakoff does in his general discussion.</p> - -<p>The histological structure of both pairs of simple eyes is the -same. Sections and macerations give me evidence of only one kind -of cells, all pigmented alike (except, of course, the non-pigmented -secondary invaginations just noted). The cells in these eyes are -very closely crowded so that their nuclei lie at several different -levels. That they all extend to the lumen of the eyes and are all -pigmented could be demonstrated with certainty in many sections, -when some of these cells whose nuclei lay most centrad could be -followed with the greatest nicety to the lumen (<a href="#plate2">Fig. 12</a>). Macerations -(<a href="#plate1">Figs. 8</a>, unlettered cells <a href="#plate3">21</a>) also show cells with very long cell bodies -pigmented at their distal ends and occasionally with a distal process -or fiber. While there are, therefore, spindle-shaped cells found, yet -they are in every other respect alike, and their differences of shape -and position of nuclei are simply the result of crowding. There is, -therefore, no evidence of supporting (pigmented) cells and spindle-shaped -visual cells (pigmented only externally) as Claus and -Schewiakoff have described and which Conant and myself cannot -corroborate.</p> - -<p>Distally, the retinal cells of the simple eyes have each a fiber -(flagellum) that extends into the lumen (Figs. <a href="#plate2">12</a>, <a href="#plate2">15</a>, <a href="#plate2">16</a>, <a href="#plate3">21</a>). Each -flagellum has a dumbbell-shaped basal body just on its entrance into -its cell quite like the basal bodies described for the visual cells of -the complex eyes (<a href="#plate2">Fig. 12</a>, part left unpigmented). Each flagellum, -or fiber, can usually be seen to extend into the cell. In one series I -found appearances like <a href="#plate2">Fig. 16</a>, which is a drawing of a part of a -section through one of the proximal simple eyes. This section is<span class="pagenum"><a name="Page_63" id="Page_63">[63]</a></span> -quite in the angle between the proximal complex eye and the group -of network cells in the upper part of the club. In this series I -could very definitely trace the distal fibers of the retinal cells -centrad, past the nucleus and into the subretinal nerve-tissue. -These fibers could be so easily followed that no doubt can exist as -to the fact noted. It thus appears that the axial fibers just -described pass centrad through the cells and are continued as nerve -fibers. On the evidence of such sections as <a href="#plate2">Fig. 16</a> I have indicated -these fibers as extending centrad through their cells. The lumen of -the simple eyes is filled with a homogeneous vitreous secretion. -This is often incomplete in some parts; occasionally the secretion -shows a formation of globules, but all this I believe to be due to -the action of reagents. Indeed, I have found simple eyes in which -hardly any secretion was present, while others showed an almost -completely filled cavity. In that portion of the vitreous secretion -just outside the mouth of the distal eyes I occasionally found numbers -of very darkly staining granules. I suspect that these are either -bacterial or algal organisms.</p> - -<p>As already noted, Claus and Schewiakoff describe two kinds of -cells for the retinas of these eyes which neither Conant nor myself -can demonstrate. Further, I believe I have shown that only one kind -exists. If any doubt should still exist, a section like <a href="#plate3">Fig. 25</a> (which -is from the epithelium of the club, but similar smaller areas with -central dots could often be demonstrated in transverse sections of the -retinal cells of the simple eyes) I believe should be convincing. -Schewiakoff further describes flagella for the retinal cells (his visual -cells) of the simple eyes quite as I have described them for all the -cells. The pigmentation that Schewiakoff mentions as occurring in -the secretions within the lumina of these eyes I believe to have -been dissolved in from the pigmented zones. I find no definite pigmentation -in these vitreous secretions. These secretions are evidently -products of the retinal cells and have been so regarded by former -observers.</p> - -<p class="section"><i>Lithocyst and Concretion.</i>—The cavity filled by the concretion is -lined in places by a single layer of cells, two of which are shown in -<a href="#plate1">Fig. 7</a>. This fact has been noted by both H. V. Wilson and Conant. -Such cells are evidently remnants of the cells that formed the concretion. -The supporting lamella completely surrounds the cavity of -the concretion.</p> - -<p><span class="pagenum"><a name="Page_64" id="Page_64">[64]</a></span></p> - -<p>The concretion filling the lithocyst has the shape of a hemiprolate -spheroid cut in the plane of the axis of revolution. Whether -it is of endo- or of ectodermal origin, I believe developmental studies -only can determine. Tests made in the Chemical Laboratory show -the presence of calcium sulphate with perhaps a very small trace of -phosphate.<a name="FNanchor_9" id="FNanchor_9"></a><a href="#Footnote_9" class="fnanchor">[i]</a> Nitric acid slowly dissolves these concretions, but I -believe Claus was mistaken when he said that they dissolve with an -evolution of gas. I watched them dissolve under the microscope, and -never could see the least bit of gas formed. If Claus’s observation is -correct, then the composition of the concretions of C. marsupialis is -different from that of the concretions of C. Xaymacana. The concretions, -further, were dissolved out of the material preserved in formaline -and in osmic acid solutions. For dissolving them in situ I used either -nitric or hydrochloric acid, or both. A slight husk remains after all -the lime is dissolved.</p> - -<p class="section"><i>The Epithelium of the Clubs.</i>—The epithelium is thickest on the -dorsal side of a club. The thickening here, as in several other -places, seems to be due to a crowding of the cells, in consequence of -which the nuclei come to lie at different levels, but I believe that all -the cells quite reach the surface. The cells with their nuclei nearest -the surface are pyramidal in shape, with the bases of the pyramids -toward the surface, while those cells whose nuclei lie deeper (where -several layers of nuclei occur) may be spindle-shaped (Figs. <a href="#plate2">12</a>, <a href="#plate3">23, -24, 26</a>). Centrad these cells are continued into a single process, which -often seems to extend to the basement membrane (Figs. <a href="#plate1">7</a>, <a href="#plate2">12, 13</a>, <a href="#plate3">23, -24</a>). Where the epithelium covers the region of the concretion, the -cells become flattened and with the long axis of their nuclei parallel -with the surface of the club (<a href="#plate1">Fig. 7</a>). The same holds true for the -corneal epithelium (Figs. <a href="#plate1">7</a>, <a href="#plate2">13</a>).</p> - -<p>It is a significant fact that in many places the nuclei form only -a single layer, and in such places one cannot speak of spindle-shaped -cells. I cannot find any evidence of sensory and supporting cells as -Schewiakoff describes. The fact that spindle-shaped cells may exist -is simply a physical consequence of their being closely crowded. -Conant arrived at the same conclusion.</p> - -<p>But I have another and better reason for supposing the existence<span class="pagenum"><a name="Page_65" id="Page_65">[65]</a></span> -of only one kind of cells in the epithelium. In a tangential section -taken just through the tips of the epithelial cells (<a href="#plate3">Fig. 25</a>) I find -polygonal areas with a central dot. This section does not at all agree -with Schewiakoff’s Fig. 8, in which he figures two kinds of cells. In -<a href="#plate3">Fig. 25</a> there can be no evidence of two kinds of cells, unless both -kinds have like flagella, for these dots are the transverse sections of -flagella continued within the cells (<a href="#plate3">Fig. 26</a>).</p> - -<p>The epithelium, then, is flagellate, a flagellum to a cell. Whether -there are flagella on the epithelium covering the region of the concretion, -I could not determine. But I believe that in all other parts, -excepting, of course, the corneas, it is flagellated. The fibers (flagella) -of the simple eyes are evidently the flagella of the invaginated -epithelium. Each flagellum has a basal body, and I could in many -instances determine that it was dumbbell-shaped (<a href="#plate2">Fig. 12</a>). This fact -was not always evident, however, and it was only occasionally that I -felt sure of it. Often the flagella showed only a general thickening -within the cells (<a href="#plate3">Fig. 26</a>) while, again, the thickening (basal body) -might be quite localized near the surface of the cell. Each flagellum -extends into its cell, and occasionally I could trace one clear past the -nucleus into the subepithelial nerve-tissue (<a href="#plate3">Fig. 26</a>), just as I did for -the axial fibers of the retinal cells of the simple eyes. In those -instances in which I could do this, the fibers could so clearly be -traced that little if any doubt can exist. I have thus made bold -and have drawn the flagella as continued through their cells into the -subepithelial nerve-tissue for all the cells of the epithelium of <a href="#plate2">Fig. 12</a>.</p> - -<p>A word on the epithelium covering the network cells of <a href="#plate2">Fig. 13</a>. -Conant and Schewiakoff here describe fibers from the supporting -lamellæ that pass in bundles in among the network cells. These -fibers are supposed to be a part of the supporting lamella which -reaches out to be a support for the epithelial cells. (Schewiakoff also -describes similar fibers for other parts of the epithelium.) Now, as -Conant himself shows in <a href="#plate2">Fig. 13</a>, these coarse fibers are not of the -same consistency and staining capacity as the supporting lamella. I -found them to stain just like the intracellular parts of the flagella or -like the central continuations of the axial fibers of the cells of the -simple eyes. I could, also, occasionally trace them to the surface of -the epithelium, and beyond, when they became continued as short -blunt processes or flagella (<a href="#plate2">Fig. 13</a>). I, therefore, conclude that they -are sensory fibers like those I have described for the other epithelial<span class="pagenum"><a name="Page_66" id="Page_66">[66]</a></span> -cells. Yet, that they pass to the supporting lamella, just as Conant -shows in <a href="#plate2">Fig. 13</a>, would seem to indicate that they are fibers from -the supporting lamella or processes of the epithelial cells. While this -stands as an objection to their being sensory fibers, yet I cannot -explain away their being continued distally as a flagellum, except I -assume this continuation to be an artefact. This does not seem -probable. Perhaps they serve both purposes; namely, that the cell -body with its axial fiber is continued to the supporting lamella, the -cell proper ending there, while the axial fiber is continued as a nerve -fiber. I believe this to be the proper explanation.</p> - -<p>The epithelium of the peduncle is quite like the epithelium of the -club just described. Sections through the tips of the epithelial cells -of the peduncle and also sections sagittal to the axis of these cells -give sections like <a href="#plate3">Figs. 25 and 26</a>. I, therefore, conclude that this -epithelium is a sensory flagellate epithelium like that of the clubs. -Nerve tissue and unstriped muscle fibers underly the epithelium of -the peduncles. Claus and Conant also describe a small ventral endodermal -tract of nerve tissue, which according to Conant is connected -with the endodermal nerve tissue found in the region of the radial -ganglia.</p> - -<p>To sum up, the epithelium of the club and the peduncle is a -flagellate sensory epithelium whose flagella are continued through -the cells as nerve fibers into the nerve tissue below. <i>A priori</i>, -judging from the mass of nerve tissue underlying the epithelium, -we should expect the epithelium to be one strictly sensory. What -sense it serves is difficult to surmise. In the physiological part of -this paper I suggested that it might be tactile, serving in connection -with the lithocysts in giving the animal sensations of space relations.</p> - -<p>Claus mentions having seen patches of flagella on the epithelium -of the clubs. Schewiakoff supposes that his spindle-shaped sensory -cells have only a single flagellum, while his supporting cells have -many cilia. In the latter supposition he was evidently mistaken. -Conant (from an unpublished note) saw the flagella of the epithelium -on the living object and does not think that there could be more -than a single one to each cell. He also concludes from living specimens -squeezed out under a cover-glass, that there is only one kind -of cells in the ectoderm.</p> - -<p>Cilia and flagella extending into the cells to which they are -attached are described by a number of observers.</p> - -<p><span class="pagenum"><a name="Page_67" id="Page_67">[67]</a></span></p> - -<p>I shall not endeavor to discuss the subject further, but shall -append the literature on the subject that has come to my notice. -(See <a href="#LITERATURE">Literature</a>). Some of these observers ascribe a nervous function -to these centrad continuations. I am inclined to believe that they -represent the primitive fibrils of Apathy, whether the cilia or flagella -are motile or sensory. I should mention, however, that Apathy has -traced the “Primitivfibrillen” to be continuous with cilia, and also -traces them into the sensory rods of the sensory cells in the sense -organs of leeches. Eimer also describes cilia as continued centrad.</p> - -<p class="section"><i>The Network Cells and the Multipolar Ganglion Cells.</i>—Conant is -the first to accurately describe the true structure of the network -cells (<a href="#plate2">Fig. 13</a>) that fill the upper part of the club between the -proximal complex eye and the attachment of the peduncle. I cannot -add anything to Conant’s description. As their name implies, they -are filled with a coarse network-like structure with a central nucleus -and nucleolus. Schewiakoff erroneously described them as ganglion -cells and Claus as supporting cells. I have sometimes thought that -they are not made up of a network, but of a vesicular structure; -<i>i. e.</i> the network we see is really produced by the sections of -planes that intersect to form little polyhedral cavities. I could not, -however, satisfy myself on this point. I further saw similar but -smaller cells, with a finer network, disposed in small groups laterally -and distally from the attachment of the peduncle to the club.</p> - -<p>What the function of these network cells is can only be guessed. -In size and shape they somewhat resemble some of the cells found -in luminous organs. Conant, however, nowhere mentions that -Charybdea is luminous.</p> - -<p>Lateral to the larger group of network cells lie two groups of -large multipolar ganglion cells (a group on each side). Claus -describes these cells, but Schewiakoff does not specially note them, -and evidently considered them a part of the network cells, which -he erroneously described as ganglion cells.</p> - -<p class="section"><i>The Nerve Tissue.</i>—I cannot add anything new on this. It -consists of fine fibers and ganglion cells, quite as described by Claus, -Schewiakoff, and Conant, and fills the club between the ampulla -and the epithelium, except the spaces occupied by the eyes, lithocyst, -and network cells. It is likewise present under the ectoderm of the<span class="pagenum"><a name="Page_68" id="Page_68">[68]</a></span> -peduncle, where also a small tract is found under the endoderm. -(See preceding head, or Claus<span class="fnanchor"><a href="#book3">[3]</a></span>, and Conant<span class="fnanchor"><a href="#book8b">[8b]</a></span>). As already noted, -under the distal complex eye, I find only large nuclei to represent -the ganglion cells. By saying this, however, I do not wish to dispute -their ganglionic nature. The large multipolar ganglion cells I have -noted under the preceding topic.</p> - -<p class="section"><i>The Supporting Lamella.</i>—The supporting lamella is a continuation, -through the peduncle, of the jelly of the bell. It completely -surrounds the ampulla and the lithocyst, and also forms a partition -between them, so that, as already noted, the lithocyst becomes -completely surrounded by it. It also sends a partition ventrally -between the complex eyes (Figs. <a href="#plate1">7</a>, <a href="#plate2">13</a>). Its thickening to form a -support for the lens of the proximal complex eye has already been -noticed. I shall limit myself in the discussion of the supporting -lamella to the above short resumé, since Schewiakoff gives further -detail.</p> - -<p class="section"><i>The Endothelium of the Ampulla and the “Floating Cells.”</i>—The -ampulla is lined by a secreting epithelium. This is shown by the -large masses of a secretion within the bases of the cells, and by -smaller masses scattered in the central and more distal parts -(Figs. <a href="#plate1">7</a>, and <a href="#plate3">27</a>, lower half). The section of the cells is such in <a href="#plate1">Fig. -7</a>, that the bases of some (those nearest the supporting lamella) are -taken, the central nuclear region of others, and the tips of those -farthest from the supporting lamella. The section may be said to be -taken diagonally through the bases and central parts of some of the -cells, but owing to the curvature of the ampulla wall, through the -tips of others. The secretion is a colloid substance, staining yellowish -gray with iron-hæmatoxylin, blue with Lyons blue, and reddish -with borax-carmine. Sometimes darkly staining rods and fibers of -unknown origin could be seen within the larger masses of the -secretion (<a href="#plate1">Fig. 7</a>). These rods and fibers could also be seen in -spaces within the cells, from which the secretion had evidently been -dissolved. I think there can be no question but that the masses -described are a secretion. Many series, however, do not show it; -indeed, an examination of Conant’s slides gave me little evidence -of a secreting function, though I could demonstrate it in his sections -both within the endothelium and also the floating bodies. The<span class="pagenum"><a name="Page_69" id="Page_69">[69]</a></span> -presence or absence of this secretion is evidently correlated with the -feeding habits of the animals, or else it would be more generally -present.</p> - -<p>The endothelium is thickest (the cells are longest) in the upper -part of the ampulla where the supporting lamella approaches the -lens of the proximal complex eye, and in the lower portion of the -ampulla (<a href="#plate1">Fig. 7</a>), in the angle between the concretion cavity and -the region of the distal complex eye. In general, the cells are -longest in the upper part of the ampulla, while in the lower part, -especially where they cover the concretion cavity and the dorsal -wall, they may be quite cubical instead of columnar. Often they -present a vacuolated appearance at their bases (<a href="#plate3">Fig. 27</a>). Claus and -Schewiakoff describe and figure this endothelium, but not in detail. -No one, to my knowledge, has described this secretory function.</p> - -<p>The nuclei of these cells are peculiar. They may contain a -network with a nucleus (<a href="#plate3">Fig. 27</a>). Again, they may show evidence -of amitotic division (<a href="#plate2">Fig. 20</a>, h, i, j). Indeed, Remak’s scheme (Wilson<span class="fnanchor"><a href="#book18">[18]</a></span> -“The Cell,” p. 46) can be quite readily demonstrated. It is, -however, such dumbbell-shaped, elliptical, or ringed nuclei as seen -in Figs. <a href="#plate1">7</a> and <a href="#plate2">20</a> that are of special interest.</p> - -<p>I have spoken of some of these nuclei as dumbbell-shaped, -elliptical, or ringed. This is so, however, only in sections. They are -really flattened spheres with a rod of tissue, of the same structure -as the nuclear wall, stretching between the poles. One may conveniently -compare the shape of these nuclei with that of an apple, -the core of the apple representing the rod connecting the two opposite -flattened or slightly hollowed poles of the nucleus. For convenience -I shall call the rod connecting the two poles the axis of the -nucleus. The dumbbell or elliptical shape would be obtained by a -meridional section through the axis (Figs. <a href="#plate2">20</a>, a, b, c, e, g, k, l, m, n, -o, <a href="#plate1">7</a>). Likewise a ringed appearance with a central dot would be -obtained by a section parallel with the flattened surfaces or perpendicular -to the axis (Figs. <a href="#plate2">20</a>, d, <a href="#plate1">7</a>). In a section not strictly meridional -the axis would be cut as in <a href="#plate3">Fig. 29</a>, a, or not show at all. As nearly -as I could determine, the inside of these nuclei is a vacuole, which -the axis penetrates.</p> - -<p>The walls and axis of these nuclei have the structure of a very -fine and dense network that stains very dark with iron-hæmatoxylin. -It stains quite like the reticulum of any nucleus, but is very dense,<span class="pagenum"><a name="Page_70" id="Page_70">[70]</a></span> -as though all the reticulum of the nucleus had been crowded together -at the surface. Judging from appearances like p (<a href="#plate2">Fig. 20</a>), the -hollowing out, so to speak, of these nuclei, would seem to be a -process of vacuolation, the reticulum becoming crowded aside to the -surface. But how, on this view, to amount for the formation of the -axis, I do not know. Perhaps the axis is formed by a pushing in of -two opposite poles of a nucleus, the two invaginations meeting and -fusing. On this supposition one might expect the axis to be hollow -(cylindrical), but I could not determine that it was. Perhaps the -centrosphere (or spheres) (see the next paragraph) has something to -do with the formation of the axis (<a href="#plate2">Fig. 20</a>, b, g, e, etc.).</p> - -<p>In the nuclei of <a href="#plate2">Fig. 20</a> with the dark outlines, and of <a href="#plate1">Fig. 7</a> -a small reticular body is seen just opposite one end of the axis, or -opposite both ends in g. In d (<a href="#plate2">Fig. 20</a>) this body is seen next the -axis just below (outside) the hollow cup represented by the hollow -ring. In this instance a central granule is seen in the reticular -body, as also in c. I take this reticular body to be the centrosphere, -and the central granule in c and d the centrosome. In k, l, m, n, -and o (<a href="#plate2">Fig. 20</a>), which are from another series, in which the walls -of the nuclei did not stain so dark as in the other nuclei of the -same figure, a nucleolus could be definitely seen, indeed, sometimes -quite perched upon the wall of the nucleus (k, l). In several -instances I could see two nuclei, as in o. But besides these nucleoli, -I could in several instances see quite definitely a reticular body -(centrosphere) opposite the axis (m, n, o) quite as I described for the -nuclei with the dark outlines. In a, b, c, d, e and g the nuclei could -not be so readily demonstrated, but I could occasionally see a darker -stained body as in a, c and g, that I have no doubt is the nucleolus, -which here, again, is perched quite upon the surface of the nucleus. -This position of the nucleolus is perhaps due to its having been -crowded to one side by the nucleus becoming hollow. It is no -uncommon thing, either, to find several nuclei in a single cell, -sometimes in process of division or just divided as o and e (<a href="#plate2">Fig. 20</a>), -also h, i and j. The whole nuclear phenomenon that I have described -seems to be one of division. Perhaps it is somehow associated with -the giving off of the secretion of the cells, for these nuclei seem to -be found in greatest abundance in those cells in which the secretion -is most abundant. In Conant’s sections I found but little evidence of -these nuclear phenomena as also little secretion, which all goes to<span class="pagenum"><a name="Page_71" id="Page_71">[71]</a></span> -show the association of the nuclear phenomenon with the secretion. -I have failed to find any descriptions in the literature of nuclei to -which I could refer my observations.</p> - -<p>The endothelium of the ampulla is flagellated (Figs. <a href="#plate1">7</a>, <a href="#plate2">17</a>, <a href="#plate3">27</a>). -It will be seen that there are two slender flagella to a cell. Each -pair of flagella has a pair of basal bodies that are longer than thick, -and which are continued as a thin fiber towards the nucleus of the -cell. That these centrad continuations of the basal bodies extend to -or past the nucleus I could not determine. Sometimes the basal -bodies with the centrad continuations are pushed quite to one side -of the cell (<a href="#plate3">Fig. 27</a>), while in other cells they are applied quite to the -distal surface (Figs. <a href="#plate1">7</a>, <a href="#plate2">17</a>, <a href="#plate3">27</a>). <a href="#plate2">Fig. 17</a>, and the part of <a href="#plate1">Fig. 7</a> that -shows these points, are taken just through the tips of the cells. The -darker lines within the polygonal areas are the intracellular basal -bodies with their centrad continuations, while the thinner lines are -the flagella, and are supposed to lie in the plane just below the -plane of the figure. In those instances in which the centrad continuations -are applied to the distal surface of the cells they could -occasionally be seen to bend centrad (<a href="#plate3">Fig. 27b</a>). While these cilia with -their basal bodies and centrad continuations are usually separate, as -shown in the figures, yet they are at times applied quite closely to -each other so that the double nature of the basal bodies and their -centrad continuations is not evident. When the intracellular continuations -of the cilia become pushed to one side or applied to the -distal surface of the cells, I believe this to be due to the turgor of -the cells consequent upon the deposition of large masses of secretion -within them. But I must add that this explanation is not altogether -satisfactory, since in the endoderm cells of the pedalia of -both Charybdea and Tripedalia I found like conditions with no evidence -of a secreting function. (See below, under tentacles.) No one, -to my knowledge, has described the flagellation in detail, although -both Claus and Schewiakoff state that the endoderm is ciliated.</p> - -<p>The “floating cells” in the stomach pockets and in the ampulla, -described by Conant, I believe are in part derived from the endothelial -cells of the ampulla. That a portion of them may arise from -the ovary, as Conant explains, I do not doubt; I have, further, found a -mass of floating cells in a small Charybdea quite as Conant describes -for Tripedalia (his Fig. 71). In this Charybdea, however, I could find -no traces of any ovary. Conant speaks of larger and smaller floating<span class="pagenum"><a name="Page_72" id="Page_72">[72]</a></span> -cells, and that the smaller ones are also found in the males. This -latter fact agrees with what I have suggested, that some of the -floating cells arise in the ampulla. My chief reasons for my supposition, -however, are the following: I find globules of the secretion -of the ampulla cells in some of the floating cells and also scattered -loosely among them (<a href="#plate2">Fig. 19</a>). These globules in and among the -floating cells have the same general appearance and a similar -staining capacity as the secretion in the ampulla cells. Again, in -spaces within some of the ampulla cells I find bodies resembling the -floating cells with lumps of the secretion within them (<a href="#plate2">Fig. 18</a>). -The conclusion, therefore, lies near that some of the floating cells -originate within the cells of the ampulla, engulf within them some -of the secretion, and are then expelled into the lumen of the ampulla. -Better said, perhaps, they represent portions of the ampulla cells -with some of the secretion. I also found several instances in which -a floating cell had the appearance of being expelled from an ampulla -cell. Conant suggests for a similar observation that the cells were -about to be swallowed by the ampulla cells. I believe, however, that -my finding a secretion similar to that within the cells of the -ampulla, in some of the floating cells, as also bodies very much -like them and filled with secretion within the ampulla cells, -together with Conant’s finding floating cells in males, and finally -the observation that the floating cells are usually quite dilapidated, -never showing a healthy cell structure—all this leads me to conclude -that some of the floating cells originate from the ampulla cells, and -that they have a nutrient function in distributing the secretion. -This is quite the reverse of what Conant supposed,—that they were -taken in as nourishment by the ampulla cells. I also find what -appears to be a secretion in the endoderm of the tentacles of both -Charybdea and Tripedalia, and believe this is another source of the -floating cells. (See below, under tentacles.)</p> - -<p>I also found other very darkly staining bodies (<a href="#plate2">Fig. 19</a>) both -within the floating cells and free in the ampulla cavity, and more -numerous in the ampulla cells themselves. This again goes to show -that floating cells take their origin from the ampulla cells. What -these darkly staining bodies are, I cannot say. Perhaps they are -something akin to the “Chromatoider Nebenkörper” described by -Lenhossek (L), or they represent another kind of secretion. If these -floating cells are derived from the cells of the ampulla, the active<span class="pagenum"><a name="Page_73" id="Page_73">[73]</a></span> -nuclear division within these also receives an explanation. Some -nuclear matter can usually be observed in the floating cells.</p> - -<p class="section"><i>The Endothelium of the Peduncle.</i>—The endothelium of the peduncle -consists of flagellate columnar cells (<a href="#plate3">Fig. 27</a>, upper half). The cells -are vacuolated at their bases like some of the cells of the ampulla, -and contain a comparatively large nucleus with nucleolus. The -flagella are long and slender, quite like those described for the cells -of the ampulla, except that there is only one to each cell. The basal -bodies of the flagella are of a peculiar shape. They may be described -as a bent spindle, continuous at their distad ends with the cilia and -at their centrad ends with a fiber that can be traced quite to the -neighborhood of the nucleus. I could not trace these fibers into the -basal parts of the cells, except in one instance, and I could not be -sure of that (<a href="#plate3">Fig. 27a</a>).</p> - -<p>Another interesting observation in connection with the basal -bodies is that they are bent in one direction on one side of the canal -and in an opposite direction on the other side. In <a href="#plate3">Fig. 27</a>, which -represents a longitudinal section of the endoderm and the supporting -lamella of the dorsal (<i>i. e.</i> farthest from the eyes) side of the peduncle, -the distal ends of the basal bodies are bent towards the ampulla, -while on the ventral side they would be bent away from the ampulla. -This seems to suggest that the flagella move the contents of the -canal in one direction on the dorsal side of the canal and in an -opposite direction on the ventral side. Conant observed in living -material that bodies in the ampulla and the canal were moving -about, and that bodies within the tentacles were moving in opposite -directions at the same time. This last observation and the histological -facts just described, I believe, are mutually corroborative. Again, <i>a -priori</i>, we should expect some such mechanism as the one described -to bring about an exchange between the contents of the ampulla and -that of the stomach pockets. I have not as yet been able to demonstrate -a similar flagellate mechanism in the tentacles. Flagella and basal -bodies are present in the tentacles, but I could not determine that -the basal bodies had any definite arrangement like that shown in -<a href="#plate3">Fig. 27</a>. (See under tentacles.) I may add, yet, that the cells in the -canal of the manubrium have cilia, similar to the ones just described, -with large basal bodies, and with centrad continuations. Finally, I -am not certain but that these cells form buds at their ends quite<span class="pagenum"><a name="Page_74" id="Page_74">[74]</a></span> -like those I describe for the endothelial cells of the tentacles (see -below), and that they aid in the formation of the floating cells. I -thought I saw such buds just at the entrance of the lumen of the -peduncle into the ampulla, but could not find conclusive evidence.</p> - -<p class="section"><i>The Tentacles and the Pedalia.</i>—My observations on the tentacles -were begun with the object of demonstrating a flagellate mechanism -similar to the one described above for the endothelium of the -peduncle. While I have failed to demonstrate such a mechanism for -the tentacles, yet several interesting points came to my notice. It -will be remembered that the tentacles of the Cubomedusæ are not -directly attached to the bell, but that a blade-like portion, the -pedalium, intervenes between the tentacles and the bell. For figures -of the pedalia and the tentacles the works of Haake, Claus, Conant -and Maas<span class="fnanchor"><a href="#book22">[22]</a></span> may be consulted.</p> - -<p class="section"><i>The Ectoderm.</i>—The ectoderm of the tentacles is the seat of a -number of differentiations. It is quite thick, as the figures (<a href="#plate3">28 and -29</a>) show, and in this respect is very different from the pedalia, on -which the ectoderm cells are quite cubical. I found evidence of cilia -here and there, but I can add nothing definite about them. Neither -can I add any definite statements regarding the ectoderm cells proper, -but what I have to say relates to their differentiations.</p> - -<p>(a) The <em>thread cells</em> are of two kinds, larger ones and smaller -ones. This is well shown in <a href="#plate3">Fig. 29</a>, which is part of a transverse -section of a tentacle of Tripedalia. Two kinds of nettle-cells are also -present in the tentacles of Charybdea, but they were specially well -shown in Tripedalia. The structure of these thread-cells seems to be -typical, and I have little more to say about them. I wish, however, -to call attention to the five or six unstriped muscle-fibers that are -attached to their basal lateral parts, and which connect them with -the basement membrane (<a href="#plate3">Figs. 28, 29</a>). Claus describes these muscle-fibers -and mentions that Fr. Müller has described them before him, -but I have not found them mentioned elsewhere in the literature of -nettle-cells. Professor Brooks tells me, however, that he has often -found them. It would appear from <a href="#plate3">Fig. 29</a> that they serve to retract -the thread-cells from the surface. Claus suggests that the muscles -are developed from the cnidoblasts.</p> - -<p>(b) The plain subectodermal <em>muscle-fibers</em> are of interest. In<span class="pagenum"><a name="Page_75" id="Page_75">[75]</a></span> -Charybdea they lie wholly enclosed within canals of the supporting -lamella (<a href="#plate3">Fig. 32</a>, upper part). They run longitudinally, and near the -base of each tentacle pass out of their canals and become strictly -subectodermal (<a href="#plate3">Figs. 31, 32</a>). This is for Charybdea. In Tripedalia -they rarely come to lie in closed canals as in Charybdea. These -facts show beyond doubt that these muscles are developed from the -ectoderm. Claus has suggested their ectodermal origin, but did not -demonstrate it. He also suggested that they become inclosed in -canals by the supporting lamella pushing up around them and finally -fusing above them. This, I believe, is demonstrated by the conditions -in Tripedalia (<a href="#plate3">Fig. 29</a>). Here the canals usually remain open, but -occasionally, as in the left-hand canal, one may become completely -inclosed. This condition of things suggests the intra-lamellar muscles -found in actiniarians. The nuclei found in the canals with the muscle-fibers -probably belong to the cells from which the muscles become -differentiated. Claus figures these muscle-fibers and nuclei, and it may -be added that the supporting lamella he figures, for C. marsupialis, -is much thicker than I have figured it for C. Xaymacana and -Tripedalia cystophora. The number of muscle-canals also is greater -and occupies a much greater depth of the thickness of the lamella. -Since Claus gives a figure of a transverse section showing the muscles -in their enclosed canals, I have not deemed it necessary to duplicate -his figure. In the transition from a tentacle to a pedalium, the -muscles are most strongly developed toward and at the edges of the -pedalium. This is true for the pedalia in general, and accounts for -the readiness with which they can be bent inwards, as noted in the -physiological part of this paper.</p> - -<p>(c) I have found a single <em>ganglion-cell</em> among the cells of the -ectoderm of the tentacles. This showed so plainly that I have figured -it (<a href="#plate3">Fig. 28</a>). Other ganglion-cells no doubt exist, but could probably -not be distinguished from other cells. In its position in <a href="#plate3">Fig. 28</a> it -appears to be associated with the nettle-cell shown just above it. Its -position is very much the same as that figured by Lendenfeld (25a).</p> - -<p class="section"><i>The Endoderm.</i>—The cells of the endoderm of a tentacle are -long and quite slender (<a href="#plate3">Fig. 31</a>). At their bases they are vacuolated -quite like the cells of the ampulla and the canal of the sensory -clubs. They contain a well-formed nucleus with a nucleolus. In -their distal half small light bodies with a dark center are very -evident. These bodies are evidently a secretion.</p> - -<p><span class="pagenum"><a name="Page_76" id="Page_76">[76]</a></span></p> - -<p>Another peculiar phenomenon presents itself in these cells. The -distal part of each cell becomes separated off from its body by what -appears to be the formation of a transverse cell-wall (<a href="#plate3">Fig. 31</a>, c-d). I -have found the ends of these cells quite separated off in some series. -The formation of the walls seems to begin as a thickening at the sides -of the cells, and a section through this region, transverse to the cells, -would appear like <a href="#plate3">Fig. 30</a>. The dots in the centers of the polygonal -areas of this figure are the centrad continuations of the cilia to be -described below. As already remarked in describing the endoderm -of the ampulla, I believe we here have another place of origin of -the “floating cells.” The secretion just described moves into the -distal parts of the cells prior to their separation (<a href="#plate3">Fig. 31</a>). In some -series I could see these secretion bodies much more numerous within -the distal ends of the cells than in <a href="#plate3">Fig. 31</a>.</p> - -<p>As will be seen in <a href="#plate3">Fig. 31</a>, each of the endoderm cells of the -tentacles has a flagellum that extends into the lumen of the tentacle. -Each flagellum has a thickening just within its cell, which may be -regarded as a basal body. From this basal body, again, a small fiber -extends centrad into each cell. It does not appear that the flagella -are thrown off with the distal parts of the cells; at all events, I never -found them connected with any of the floating cells except in a few -doubtful instances.</p> - -<p>What I have said for the endoderm of the tentacle of Charybdea -applies equally to Tripedalia.</p> - -<p>Claus, in his figure of a transverse section of a tentacle of C. -marsupialis shows the endoderm as cubical. I cannot explain why -there should be such a difference between the endoderm of the -tentacles of <i>C. marsupialis</i> and that of the tentacles of <i>C. Xaymacana</i> -and <i>Tripedalia cystophora</i>. Claus does not describe the endoderm in -detail.</p> - -<p>The endoderm cells of the pedalia of both Charybdea and -Tripedalia are cubical and possess flagella, basal bodies, and centrad -continuations, quite like those I have described for the endoderm cells -of the ampulla. The double nature of the basal bodies and the centrad -continuations is, however, not so evident. A secretion I did not find. -Histologically, therefore, the endothelium of the pedalia corresponds -rather with that of the ampulla, and that of the tentacles with that -of the peduncle of the clubs.</p> - -<p><span class="pagenum"><a name="Page_77" id="Page_77">[77]</a></span></p> - -<h3>SUMMARY.</h3> - -<p>The most important results in the histological part of this paper -relate to the structure of the retinas of the eyes of the sensory clubs.</p> - -<p>The retina of the distal complex eye is composed of three kinds -of cells: two kinds of sensory cells (the prism and pyramid cells), -and the long pigment cells (<a href="#plate1">Figs. 1-9</a>). The prism and pyramid cells -have each an axial nerve fiber in their prisms and pyramids respectively. -These fibers I could, however, trace only to the neighborhood -of the nuclei. But since I could trace similar fibers in the retinal -cells of the simple eyes (<a href="#plate2">Fig. 16</a>) past the nucleus into the subretinal -nerve tissue, I believe that the axial fibers in question also extend -centrad as nerve fibers into the subretinal nerve tissue. Other observers -also figure such fibers as extending centrad as nerve fibers. The axial -fibers of the prism cells have each a dumbbell-shaped basal body at -their entrance into the pigmented part of a cell. The evidence for a -body of such shape in the pyramid cells was not conclusive, though -a basal body for the axial fiber exists. The long pigment cells project -or retract their pigment in light or darkness respectively and thus -seem to serve to check the diffusion of light in the retina. I have -also supposed that these cells may serve for conducting impulses to -the lens, and that the latter is adjustable.</p> - -<p>The proximal complex eye (<a href="#plate2">Fig. 13</a>) has only the prism cells -present in its retina, and not two kinds of cells as Schewiakoff has -described (see text, pp. <a href="#Page_53">53</a>, <a href="#Page_60">60</a>, <a href="#Page_63">63</a>) for all the eyes.</p> - -<p>The simple eyes (<a href="#plate2">Fig. 12</a>), two on each side of a club, four in -all, also have only one kind of cells in their retinas, and each cell -has a flagellum extending into the vitreous secretion of the lumen. -These flagella could be traced centrad as a nerve fiber (<a href="#plate2">Figs. 12, 16</a>). -Similarly, a nerve fiber could be traced centrad from the flagella of -the epithelial cells of the clubs. Dumbbell-shaped basal bodies for -the flagella of the simple eyes could also be demonstrated, but the -evidence for this in the epithelial cells of the clubs was not so -satisfactory.</p> - -<p>Other points of interest are: A secretory epithelium lining the -ampulla of the clubs, and a somewhat similar epithelium lining -the canals of the tentacles (Figs. <a href="#plate1">7</a>, <a href="#plate3">27, 31</a>); the partial origin of the -“floating bodies” in the canals of the clubs and tentacles and the -stomach pockets from these epithelia (<a href="#plate2">Figs. 18, 19</a>); two flagella to<span class="pagenum"><a name="Page_78" id="Page_78">[78]</a></span> -each cell of the endothelium of the ampulla and of the pedalia (Figs. -<a href="#plate1">7</a>, <a href="#plate2">17</a>); the peculiar nuclei in the endothelial cells of the ampulla -(<a href="#plate2">Fig. 20</a>); the longitudinal muscles of the tentacles being completely -inclosed within canals of the supporting lamella, but near the base -of a tentacle becoming subectodermal. This demonstrates their -ectodermal origin. In Tripedalia it is seldom that any of these -muscles become enclosed as in Charybdea (<a href="#plate3">Fig. 29</a>).</p> - -<p>If to the reader my results seem to embody a somewhat heterogeneous -detail, he must remember that the work consists partly -in corroborating and partly in supplementing the work of previous -observers, and that, in general, histological detail does not usually -make the most readable paper.</p> - -<p class="smaller"><span class="smcap">Biological Laboratory, -Johns Hopkins Univ.</span>, May 1899.</p> - -<hr /> - -<div class="footnotes"> - -<h2>FOOTNOTES</h2> - -<div class="footnote"> - -<p><a name="Footnote_1" id="Footnote_1"></a><a href="#FNanchor_1"><span class="label">[a]</span></a> It was at one time supposed that the concretions in the marginal bodies of -medusæ represented lenses and the surrounding nerve tissue the optic nerve, a -supposition so highly improbable that it never gained any acceptance. (Ib., p. -41, note.)</p> - -</div> - -<div class="footnote"> - -<p><a name="Footnote_2" id="Footnote_2"></a><a href="#FNanchor_2"><span class="label">[b]</span></a> Eimer’s results I get from Romanes and Hesse<span class="fnanchor"><a href="#bookIII">[III]</a></span>.</p> - -</div> - -<div class="footnote"> - -<p><a name="Footnote_3" id="Footnote_3"></a><a href="#FNanchor_3"><span class="label">[c]</span></a> By no means do I wish to attribute intelligence to these animals.</p> - -</div> - -<div class="footnote"> - -<p><a name="Footnote_4" id="Footnote_4"></a><a href="#FNanchor_4"><span class="label">[d]</span></a> Haake<span class="fnanchor"><a href="#book2">[2]</a></span> says that in the adult <i>Charybdea Rostonii</i> the vitreous bodies of -the complex eyes are absent but present in the young. It is difficult to -explain this observation except on grounds of imperfect preservation of the -adult material, for in all observations on other forms a vitreous body is -described. Haake evidently did not use sections, and for this reason his -results must be regarded as of doubtful accuracy. Haake also says that the -simple lateral eyes of the clubs are absent in the adult, but present in the -young.</p> - -</div> - -<div class="footnote"> - -<p><a name="Footnote_5" id="Footnote_5"></a><a href="#FNanchor_5"><span class="label">[e]</span></a> In the series from which <a href="#plate1">Fig. 3</a> is taken the pyramid-cells are not so -readily demonstrated. Indeed, I missed them altogether at first in this and -some other series and supposed that there were only two kinds of cells (<a href="#plate2">19</a>), -but upon a careful re-examination I could demonstrate them to my satisfaction. -They did not show, however, in the particular section of <a href="#plate1">Fig. 3</a>, so that they -are not indicated in this figure.</p> - -</div> - -<div class="footnote"> - -<p><a name="Footnote_6" id="Footnote_6"></a><a href="#FNanchor_6"><span class="label">[f]</span></a> I go into this at some length because the cell-walls in the series that -showed the nuclei best differentiated as lighter and darker ones did not show -well, and there might be some doubt that these lighter nuclei belonged to the -pyramid cells. I could, however, in many instances, trace the axial fibers of -the pyramids through the pigmented zone to these lighter nuclei (as already -noted) which fact can leave no doubt but that some of these nuclei belong to -the pyramid cells. (Similar nuclei, however, are found to belong to the long -pigment cells, to be described below.) Centrad these pyramid cells are continued -into a single process just as the prism cells were shown to be (<a href="#plate1">Fig. 7</a>). Figures -<a href="#plate1">6, 8, 9</a>, and <a href="#plate2">21</a> show samples of all the pigmented cells found in macerated -preparations, and none of these (except <a href="#plate1">Fig. 9</a>, long pigment cells) show more -than a single centrad process. Hence, I conclude that centrad both the pyramid -cells and prism cells are continued as a single prolongation.</p> - -</div> - -<div class="footnote"> - -<p><a name="Footnote_7" id="Footnote_7"></a><a href="#FNanchor_7"><span class="label">[g]</span></a> I have been able to demonstrate nucleoli in all the different nuclei of the -cells of the sensory clubs.</p> - -</div> - -<div class="footnote"> - -<p><a name="Footnote_8" id="Footnote_8"></a><a href="#FNanchor_8"><span class="label">[h]</span></a> It may be objected that my criterion, the presence of axial fibers, is not -necessarily characteristic of visual cells. However, the great general occurrence -of such axial fibers (Patten,<span class="fnanchor"><a href="#book5a">[5]</a></span> Grenacher,<span class="fnanchor"><a href="#book16">[16]</a></span> Schreiner,<span class="fnanchor"><a href="#book12a">[12]</a></span> Hesse,<span class="fnanchor"><a href="#book13">[13]</a></span> myself, in simple -complex eye, see below, and perhaps others) in eyes in which the retina has -only one kind of cells, would seem to indicate that they are quite characteristic -of visual cells. Note again that in the proximal eye of Charybdea there -is only one kind of cells and with axial fibers.</p> - -</div> - -<div class="footnote"> - -<p><a name="Footnote_9" id="Footnote_9"></a><a href="#FNanchor_9"><span class="label">[i]</span></a> Mr. J. C. Olsen, of the Chemical Laboratory, kindly made these tests for me.</p> - -</div> - -</div> - -<hr /> - -<h2 id="LITERATURE">LITERATURE.</h2> - -<h3>LITERATURE REFERRED TO IN THE SECTION ON PHYSIOLOGY.</h3> - -<p id="bookIa">I. <span class="smcap">Romanes</span>, G. J. a. ’75, ’77. The Locomotor System of Medusæ. Philosophical -Transactions. London. Vol. CLXVI, pt. 1. Vol. CLXVII, pt. 2.</p> - -<div class="blockquote"> - -<p id="bookIb">b. ’85. Jelly-fish, Star-fish and Sea-urchins. London.</p> - -</div> - -<p id="bookII">II. <span class="smcap">Murbach, Louis</span>. ’95. Preliminary Notes on the Life-history of Gonionemus. -Journal of Morphology. Vol. XI.</p> - -<p id="bookIII">III. <span class="smcap">Hesse, R.</span> ’95. Über das Nervensystem und die Sinnesorgane v. Rhizostoma -Cuvieri. Zeit. Wis. Zool., B. LX.</p> - -<p id="bookIV">IV. <span class="smcap">Eimer, Th.</span> Zoologische Untersuchungen. ’74. Würzburg Verhandlungen. -VI. Bd.</p> - -<p id="bookV">V. <span class="smcap">Haeckel, E.</span> ’79. Monographie der Medusen. Jena.</p> - -<p id="bookVI">VI. <span class="smcap">Berger, E. W.</span> ’98. Abstract of Dr. F. S. Conant’s Notes on the Physiology -of the Medusæ. Johns Hopkins University Circulars. Vol. XVIII, No. 137.</p> - -<p id="bookVII">VII. (See also <a href="#book8a">8</a>, below.)</p> - -<h3>LITERATURE REFERRED TO IN THE SECTION ON HISTOLOGY.</h3> - -<p id="book1">1. <span class="smcap">Carrière, J.</span> ’85. Die Schorgane der Thiere. München u. Leipzig.</p> - -<p id="book2">2. <span class="smcap">Haake, W.</span> ’87. Scyphomedusen des St. Vincent Golfes. Jen. Zeit. f. -Naturwis., Bd. XX., pp. 596-597, 602-604.</p> - -<p id="book3">3. <span class="smcap">Claus, C.</span> ’78. Über Charybdea marsupialis. Arb. aus dem Zool., Inst. -Univers. Wien., Bd. I.</p> - -<p id="book4">4. <span class="smcap">Schewiakoff, W.</span> ’89. Beiträge zur Kenntniss des Acalephenauges. Morph. -Jahrb., Bd. XV, H. 1.</p> - -<p id="book5a">5. <span class="smcap">Patten, William.</span> a. ’89. Studies on the eyes of Arthropods. II. Eyes of -Acilius. Journal of Morphology. Vol. II.</p> - -<div class="blockquote"> - -<p id="book5b">b. ’98. A Basis for a Theory of Color Vision. American Naturalist. Vol. -XXXII, No. 383.</p> - -</div> - -<p><span class="pagenum"><a name="Page_79" id="Page_79">[79]</a></span></p> - -<p id="book6">6. <span class="smcap">Apathy, St.</span> ’97. Das Leitende Element des Nervensystems u. seine topographischen -Beziehungen zu den Zellen. Mitt. Zool. Stat. Neapel., Bd. XII, H. 4.</p> - -<p id="book7">7. <span class="smcap">Parker, G. H.</span> ’97. Photomechanical Changes in the Retinal Pigment Cells -of Palæmonites, and their Relation to the Central Nervous System. Bull. Mus. -Comp. Zool. Harvard Coll. Vol. XXX, No. 6.</p> - -<p id="book8a">8. <span class="smcap">Conant, F. S.</span> a. ’97. Notes on the Cubomedusæ. Johns Hopkins University -Circulars. Vol. XVII, No. 132.</p> - -<div class="blockquote"> - -<p id="book8b">b. ’98. The Cubomedusæ. Memoirs Biological Laboratory Johns Hopkins -Univ. Vol. IV, No. 1.</p> - -</div> - -<p id="book9">9. <span class="smcap">A Review of</span> <a href="#book5b">5b</a>. ’99. A Theory of Color Vision. Natural Science. Vol. -XIV, No. 85.</p> - -<p id="book10">10. <span class="smcap">Herrick, F. H.</span> ’91. The Embryology and Metamorphosis of the Macroura -(Brooks and Herrick). Natl. Acad. Sciences. Vol. V, p. 454.</p> - -<p id="book11">11. <span class="smcap">Hertwig</span>, O. & R. ’78. Das Nervensystem und die Sinnesorgane der -Medusen. Leipzig.</p> - -<p id="book12a">12. <span class="smcap">Schreiner, K. E.</span> a. ’96. Die Augen bei Pecten und Lima. Bergens -Museums Aarbog.</p> - -<div class="blockquote"> - -<p id="book12b">b. ’97. Histologische Studien über die Augen der freilebenden marinen -Borstenwürmer. Bergens Museums Aarbog.</p> - -</div> - -<p id="book13">13. <span class="smcap">Hesse, R.</span> ’99. Untersuchungen über die Organe der Lichtempfindung bei -niederen Thieren. V. Die Augen der Polychäten Anneliden. Zeit. Wis. Zool., -B. LXV, H. 3.</p> - -<p id="book14">14. <span class="smcap">Andrews, E. A.</span> ’92. On the Eyes of Polychætous Annelids. Journal of -Morphology. Vol. VII.</p> - -<p id="book15">15. <span class="smcap">Wilson, H. V.</span> ’78. Unpublished Notes.</p> - -<p id="book16">16. <span class="smcap">Grenacher, H.</span> ’84. Abhandlungen zur vergleichenden Anatomie des -Auges. I. Die Retine der Cephalopoden. Abhandl. der Naturf. Gesellsch. zu Halle. -Bd. XVI.</p> - -<p id="book17">17. <span class="smcap">Beer, Theodore.</span> ’98. Die Accomodation des Auges in der Thierreihe. -Wiener klinische Wochenschrift. Nr. 42.</p> - -<p id="book18">18. <span class="smcap">Wilson, E. B.</span> ’96. The Cell.</p> - -<p id="book19">19. <span class="smcap">Berger, E. W.</span> ’98. The Histological Structure of the Eyes of Cubomedusæ. -The Journal of Comp. Neurology. Vol. VIII, No. 3.</p> - -<p id="book20">20. <span class="smcap">Lendenfeld, R.</span> Die Nesselzellen der Chidarier. (Review and bibliography.) -Biol. Centralbl. Bd. XVII, Nr. 13.</p> - -<p id="book21">21. <span class="smcap">Schneider, K.</span> ’90. Histologie von Hydra fusca mit besonderer Berücksichtigung -des Nervensystems der Hydropolypen. Arch. Mik. Anat. Vol. XXXV.</p> - -<p id="book22">22. <span class="smcap">Maas, O.</span> ’98. Die Medusen. (Charybdea arborifera, Systematic.) Mem. -Mus. Comp. Zool., Harvard Coll. Vol. XXIII, No. 1.</p> - -<h3>LITERATURE REFERRING TO THE CENTRAD CONTINUATIONS OF CILIA AND FLAGELLA.</h3> - -<p id="bookA">A. <span class="smcap">Haeckel, E.</span> ’72. Die Kalkschwämme. Vol. I, p. 141; Vol. III, Pl. 25, -Figs. 3-5.</p> - -<p id="bookB">B. <span class="smcap">Schultze, F. E.</span> ’75. Rhizopodien Studien. V. Arch. Mik. Anat. Bd. II, p. 583.</p> - -<p><span class="pagenum"><a name="Page_80" id="Page_80">[80]</a></span></p> - -<p id="bookC">C. <span class="smcap">Eimer, Th.</span> ’77. Weitere Nachrichten über d. Bau des Zellkerns, nebst -Bemerkungen über Wimperepithelien. Arch. f. Mik. Anat. Bd. XIV, Taf. VII, p. 114.</p> - -<p id="bookD">D. <span class="smcap">Bütschli, O.</span> ’78. Beiträge zur Kenntniss der Flagellaten, u. s. w. Zeit. -f. Wis. Zool. Bd. XXX, p. 269.</p> - -<p id="bookE">E. <span class="smcap">Engelmann, Th. W.</span> ’80. Zur Anatomie u. Physiologie d. Flimmerzellen -Pflüger’s Arch. Bd. XXIII.</p> - -<p id="bookF">F. <span class="smcap">Hatschek, B.</span> ’85. Entwickelung der Trochophora von Eupomatus uncinatus -Arb. Zool. Inst. Wien., Bd. VI, p. 139.</p> - -<p id="bookG">G. <span class="smcap">Heider, K.</span> ’86. Zur Metamorphose der Oscarella lobularis. Arb. Zool. -Inst. Wien., Bd. VI, pp. 189-194.</p> - -<p id="bookH">H. <span class="smcap">Schneider, K. C.</span> ’92. Einige histologische Befunde an Coelenterata. Jen. -Zeit. f. Nat. 27, N. F. 20.</p> - -<p id="bookI">I. <span class="smcap">Hecht, Emile.</span> ’95. Contribution a l’Étude des Nudibranchs. Memoirs de -la Société Zool. de France. T. 8, Pl. IV, Fig. 45.</p> - -<p id="bookJ">J. <span class="smcap">Minchin, E. A.</span> ’96. Notes on the Larva and Postlarval Development of -Leucolosolemia variabilis, etc. Proc. R. Soc., London. Vol. LX.</p> - -<p id="bookK">K. <span class="smcap">Henneguy, L. F.</span> ’98. Sur le rapports des ciles vibrales avec les centrosomes. -Arch. d’anat. micros., T. 1.</p> - -<p id="bookL">L. <span class="smcap">Lenhossek, H.</span> ’98. Über Flimmerzellen. Anat. Anz. (Supplement.) Bd. -XIV.</p> - -<p id="bookM">M. <span class="smcap">Petre, Carl.</span> ’99. Das Centrum für die Flimmer u. Geisel-bewegung. -Anat. Anz. Bd. XV, Nos. 14 and 15.</p> - -<p id="bookN">N. <a href="#book6">See also 6.</a></p> - -<hr /> - -<h2 id="REFERENCE_LETTERS">REFERENCE LETTERS.</h2> - -<table summary="Reference letters and their meanings"> - <tr> - <td class="right">a</td> - <td class="center">=</td> - <td>flagellum in <a href="#plate3">Fig. 27</a>, that is supposed to extend centrad beyond the nucleus.</td> - </tr> - <tr> - <td class="right">b</td> - <td class="center">=</td> - <td>twin flagella in <a href="#plate3">Fig. 27</a>, of which the centrad continuation is seen applied against the distal surface of the cells and to be continued centrad.</td> - </tr> - <tr> - <td class="right">c</td> - <td class="center">=</td> - <td>capsule of lens.</td> - </tr> - <tr> - <td class="right">cf</td> - <td class="center">=</td> - <td>axial fibers of cells extending centrad.</td> - </tr> - <tr> - <td class="right">co</td> - <td class="center">=</td> - <td>cornea.</td> - </tr> - <tr> - <td class="right">concr</td> - <td class="center">=</td> - <td>concretion cavity.</td> - </tr> - <tr> - <td class="right">ec</td> - <td class="center">=</td> - <td>ectoderm.</td> - </tr> - <tr> - <td class="right">en</td> - <td class="center">=</td> - <td>endoderm.</td> - </tr> - <tr> - <td class="right">f</td> - <td class="center">=</td> - <td>flagella.</td> - </tr> - <tr> - <td class="right">flp</td> - <td class="center">=</td> - <td>distal fiber of a long pigment cell.</td> - </tr> - <tr> - <td class="right">fpr</td> - <td class="center">=</td> - <td>axial nerve fiber of a prism cell.</td> - </tr> - <tr> - <td class="right">fpyr</td> - <td class="center">=</td> - <td>axial nerve fiber of a pyramid cell.</td> - </tr> - <tr> - <td class="right">frc</td> - <td class="center">=</td> - <td>axial nerve fiber of the retinal cells of the simple eyes.</td> - </tr> - <tr> - <td class="right">gc</td> - <td class="center">=</td> - <td>ganglion cells.</td> - </tr> - <tr> - <td class="right">ind</td> - <td class="center">=</td> - <td>impression of the lens probably due to the pressure of weight against the surrounding tissue.</td> - </tr> - <tr> - <td class="right">l</td> - <td class="center">=</td> - <td>lens.</td> - </tr> - <tr> - <td class="right">lp</td> - <td class="center">=</td> - <td>long pigment cells.</td> - </tr> - <tr> - <td class="right">m</td> - <td class="center">=</td> - <td>muscle fibers.</td> - </tr> - <tr> - <td class="right">namp</td> - <td class="center">=</td> - <td>nuclei of ampulla cells.</td> - </tr> - <tr> - <td class="right">nc</td> - <td class="center">=</td> - <td>network cells (<a href="#plate2">Figs. 13 and 16</a>), and nettle cells (<a href="#plate3">Figs. 28, 29</a>).</td> - </tr> - <tr> - <td class="right">nf</td> - <td class="center">=</td> - <td>nerve fibers and tissue.</td> - </tr> - <tr> - <td class="right">nlp</td> - <td class="center">=</td> - <td>nucleus of long pigment cell.</td> - </tr> - <tr> - <td class="right">nm</td> - <td class="center">=</td> - <td>nucleus of muscle cells.</td> - </tr> - <tr> - <td class="right">nprc</td> - <td class="center">=</td> - <td>nucleus of prism cell.</td> - </tr> - <tr> - <td class="right"><span class="pagenum"><a name="Page_81" id="Page_81">[81]</a></span>npyrc</td> - <td class="center">=</td> - <td>nucleus of pyramid cell.</td> - </tr> - <tr> - <td class="right">nz</td> - <td class="center">=</td> - <td>nuclear zone.</td> - </tr> - <tr> - <td class="right">pr</td> - <td class="center">=</td> - <td>prism of prism cell.</td> - </tr> - <tr> - <td class="right">prc</td> - <td class="center">=</td> - <td>prism cell.</td> - </tr> - <tr> - <td class="right">pyr</td> - <td class="center">=</td> - <td>pyramid of pyramid cell.</td> - </tr> - <tr> - <td class="right">pyrc</td> - <td class="center">=</td> - <td>pyramid cell.</td> - </tr> - <tr> - <td class="right">pz</td> - <td class="center">=</td> - <td>pigmented zone.</td> - </tr> - <tr> - <td class="right">r</td> - <td class="center">=</td> - <td>retina.</td> - </tr> - <tr> - <td class="right">s</td> - <td class="center">=</td> - <td>secretion in endo. of tent. and ampulla.</td> - </tr> - <tr> - <td class="right">sh</td> - <td class="center">=</td> - <td>shrinkage space.</td> - </tr> - <tr> - <td class="right">sec</td> - <td class="center">=</td> - <td>vitreous secretion in the lumen of the simple eyes.</td> - </tr> - <tr> - <td class="right">sla</td> - <td class="center">=</td> - <td>supporting lamella.</td> - </tr> - <tr> - <td class="right">vb</td> - <td class="center">=</td> - <td>vitreous body or zone.</td> - </tr> - <tr> - <td class="right">x</td> - <td class="center">=</td> - <td>(1) the approximate level at which <a href="#plate1">Fig. 4</a> should be cut transversely to give <a href="#plate1">Figs. 1 and 3</a>.<br /> - (2) the thickening of the supporting lamella in <a href="#plate2">Fig. 13</a> to support the lens.</td> - </tr> - <tr> - <td class="right">*</td> - <td class="center">=</td> - <td>Point of approximation of cells of lenses in Figs. <a href="#plate1">7</a> and <a href="#plate2">13</a>.</td> - </tr> -</table> - -<hr /> - -<h2 id="DESCRIPTION_OF_FIGURES">DESCRIPTION OF FIGURES.</h2> - -<p class="center">ALL FIGURES, UNLESS OTHERWISE STATED, ARE FROM CHARYBDEA.</p> - -<p><a href="#plate1">Fig. 1</a>. This figure represents a transverse section through a portion of the -vitreous body of the distal complex eye at about the level x of <a href="#plate1">Fig. 4</a>. Three kinds -of areas are seen, namely, the prisms and pyramids with their axial fibers and the -distal continuations of the long pigment cells. Towards the lower left of the figure -the section is a little more distal than at the right and the transverse areas of the long -pigment cells are no more so large as at the right of the figure. The dark granules in -the areas of the long pigment cells represent pigment. Camera lucida sketch. ×920. -pp. <a href="#Page_45">45</a>, <a href="#Page_46">46</a>, <a href="#Page_48">48</a>, <a href="#Page_49">49</a>, <a href="#Page_50">50</a>, <a href="#Page_51">51</a>, <a href="#Page_52">52</a>, <a href="#Page_54">54</a>.</p> - -<p><a href="#plate1">Fig. 2</a>. This figure is a camera lucida sketch from a section taken transverse -through the most distal part of the pigmented zone of a slightly pigmented retina of -a distal complex eye. The presence of three kinds of elements is again evident. The -dots without the polygonal areas represent the centrad continuations of the axial fibers -of the prism cells. The lettering explains the other areas. ×920. pp. <a href="#Page_46">46</a>, <a href="#Page_48">48</a>, <a href="#Page_50">50</a>.</p> - -<p><a href="#plate1">Fig. 3</a>. This is from a section similar to that of <a href="#plate1">Fig. 1</a>, but a little more distal. -At the right, the section is more distal than at the left of the figure, in consequence -of which the long pigment cells are there taken through their distal fibers. Note the -small shrinkage spaces about the axial fibers of the prisms. The white lines bounding -the prism areas appear as in nature. The pyramid cells are not shown in this figure. -×950. Camera sketch. pp. <a href="#Page_50">50</a>, <a href="#Page_51">51</a>, <a href="#Page_52">52</a>, <a href="#Page_54">54</a>.</p> - -<p><a href="#plate1">Fig. 4</a>. This figure is from a section taken parallel to the long axis of the cells -of the retina of a distal complex eye. It is from a camera sketch, and nothing has -been put into the figure except what could be clearly seen. The lateral boundary -lines of the prisms are not shown. Note the evidence for the existence of three kinds -of cells. ×920. pp. <a href="#Page_44">44-52</a>, <a href="#Page_54">54</a>.</p> - -<p><a href="#plate1">Fig. 5</a>. This figure represents a sagittal section through the nuclear and -pigmented zones and the subretinal nerve tissue of a slightly pigmented retina of a -distal complex eye, that had been killed in the dark. Camera sketch. The pyramid -cells are not shown. ×900. pp. <a href="#Page_47">47</a>, <a href="#Page_51">51</a>, <a href="#Page_52">52</a>, <a href="#Page_53">53</a>.</p> - -<p><a href="#plate1">Fig. 6</a>. These cells are from a preparation by Conant of a sensory club, macerated<span class="pagenum"><a name="Page_82" id="Page_82">[82]</a></span> -in acetic acid. Cell a is evidently an iris cell. The others are probably prism cells -from the proximal complex eye. ×900. pp. <a href="#Page_44">44</a>, <a href="#Page_48">48</a>.</p> - -<p><a href="#plate1">Fig. 7</a>. In this figure I represent a sagittal section through the distal complex -eye. In the middle half of the section, the nuclei, the prism and pyramid cells with -their axial fibers, and the long pigment cells with their large distal fibers are all -strictly camera lucida sketched. A portion of the pigmented zone has been left -unpigmented to better show its structure. At the right and above the concretion -cavity is shown a portion of the endoderm of the ampulla. The section is not strictly -in a dorsoventral plane of the club, in consequence of which the cells of the ampulla -are cut diagonally and through their tips. Note the dumbbell-shaped nuclei of the -ampulla cells, as also the masses of secretion. A part of the retina of the proximal -complex eye is shown in the upper part of the figure. ×920. pp. <a href="#Page_41">41-54</a>, <a href="#Page_63">63</a>, <a href="#Page_64">64</a>, -<a href="#Page_68">68-71</a>.</p> - -<p><a href="#plate1">Fig. 8</a>. These cells are from a macerated preparation. Cells a, b, c, d may be -either prism or pyramid cells from the distal complex eye or prism cells from the -proximal complex eye. Cells e and f are probably from the right fourth (<a href="#plate2">Fig. 13</a>) of -the retina of the proximal complex eye or from the simple eyes. The unlettered -cells are probably from the simple eyes. Some of these show a distal process. ×900. -pp. <a href="#Page_48">48</a>, <a href="#Page_62">62</a>, <a href="#Page_65">65</a>.</p> - -<p><a href="#plate1">Fig. 9</a>. The cells here figured are long pigment cells from the same preparation -as <a href="#plate1">Fig. 6</a>. ×900. pp. <a href="#Page_50">50</a>, <a href="#Page_51">51</a>.</p> - -<p><a href="#plate1">Fig. 10</a>. This drawing shows an end view of a group of prisms from the same -preparation as <a href="#plate1">Fig. 6</a>. ×900. pp. <a href="#Page_46">46</a>.</p> - -<p><a href="#plate1">Fig. 11</a>. This group of prisms are from the same preparation as <a href="#plate1">Fig. 6</a>. Two of -them are broken off. The fibers seen at the lower end are probably some of the axial -fibers. The fiber at the upper end I believe is interprismatic and the distal fiber of a -long pigment cell. ×900. pp. <a href="#Page_46">46</a>.</p> - -<p><a href="#plate2">Fig. 12</a>. This figure is a summary of my results on the simple eyes. It is from a -camera sketch of one of the distal eyes, but somewhat diagrammatic. The left side of -the figure is proximal, the right side distal. ×920. pp. <a href="#Page_61">61</a>, <a href="#Page_62">62</a>, <a href="#Page_64">64</a>, <a href="#Page_65">65</a>.</p> - -<p><a href="#plate2">Fig. 13</a>. Sagittal dorsoventral section of a proximal complex eye. Conant drew -and published this as his Fig. 69. Conant’s evidence regarding the axial fibers of the -prism cells was incomplete; so that, in this respect, he left his figure unfinished. I -have drawn in these fibers and republish the figure. At the right of the retina and -next the lens (the white space) the vitreous body is incomplete and the fibers from the -retinal cells project freely into the space. This part of the retina also remains -unpigmented. Like my <a href="#plate1">Fig. 7</a>, this figure evidently represents a section somewhat to -one side of a sagittal dorsoventral plane of the club, so that the endoderm cells of -the ampulla are cut diagonally or transversely. pp. <a href="#Page_41">41-44</a>, <a href="#Page_60">60</a>, <a href="#Page_64">64-68</a>.</p> - -<p><a href="#plate2">Fig. 14</a>. This is drawn to show how regularly small shrinkage spaces may occur -in transverse sections of the vitreous bodies. This figure is from a transverse section -of the vitreous body of a proximal complex eye. I believe that these spaces are determined -by the axial fibers of the prisms. Prism outlines are not shown. ×950. -pp. <a href="#Page_54">54</a>.</p> - -<p><span class="pagenum"><a name="Page_83" id="Page_83">[83]</a></span></p> - -<p><a href="#plate2">Fig. 15</a>. This figure is a drawing of a portion of a transverse section of one of -the simple eyes. Note the flagella from the retinal cells. pp. <a href="#Page_62">62</a>.</p> - -<p><a href="#plate2">Fig. 16</a>. The section of the lower left hand corner of this figure is through a portion -of one of the proximal complex eyes, and shows the centrad continuation of the -axial nerve fibers of the retinal cells. The section is such, that, besides the simple -eye, the nuclei of the proximal complex eye (upper part of figure) and two network -cells are cut. ×920. pp. <a href="#Page_47">47</a>, <a href="#Page_62">62</a>, <a href="#Page_63">63</a>.</p> - -<p><a href="#plate2">Fig. 17</a>. A transverse section through the tips of the ampulla cells is here shown. -To the left is towards the upper end of the ampulla. The basal bodies with the centrad -fibers are in the plane of the section, while the flagella are supposed to extend -below the plane of the section. ×1350. pp. <a href="#Page_71">71</a>.</p> - -<p><a href="#plate2">Fig. 18</a>. These bodies, from within the ampulla cells, contain some of the secretion -of the ampulla cells, and resemble the “floating bodies.” ×1350. pp. <a href="#Page_72">72</a>.</p> - -<p><a href="#plate2">Fig. 19</a>. The “floating bodies” here represented are from the ampulla. Globules -of a secretion similar to that found in the ampulla cells are seen both within and -without the bodies. Note also the two black bodies without the cells and two or -three similar ones within the cells. These latter bodies are of doubtful nature. -×1320. pp. <a href="#Page_72">72</a>.</p> - -<p><a href="#plate2">Fig. 20</a>. This figure represents sections of the various nuclei found within the -ampulla cells. ×1350. pp. <a href="#Page_69">69</a>, <a href="#Page_70">70</a>.</p> - -<p><a href="#plate2">Fig. 21</a>. These cells are from the same preparation as <a href="#plate1">Fig. 6</a>. They are -evidently retinal cells from the simple eyes. The tendency of their pigmented -ends to become globular, I believe, is due to their having become isolated before -they hardened during maceration. ×920. pp. <a href="#Page_62">62</a>.</p> - -<p><a href="#plate2">Fig. 22</a>. This diagram illustrates the retraction of the long pigment cells. -The dotted lines in the vitreous body mark the outlines of the prisms, while -the continuous lines represent the axial fibers of the prism and pyramid cells. -pp. <a href="#Page_45">45</a>, <a href="#Page_46">46</a>, <a href="#Page_48">48</a>, <a href="#Page_49">49</a>, <a href="#Page_53">53</a>.</p> - -<p><a href="#plate3">Fig. 23</a>. These cells are from the epithelium of a sensory club. They are -from the same preparation as <a href="#plate1">Fig. 6</a>. Flagella are not shown. ×900. p. <a href="#Page_64">64</a>.</p> - -<p><a href="#plate3">Fig. 24</a>. This group of epithelial cells of a club are from the same preparation -as <a href="#plate1">Fig. 6</a>. ×850. p. <a href="#Page_64">64</a>.</p> - -<p><a href="#plate3">Fig. 25</a>. This sketch is a transverse section through the tips of the epithelial -cells of a club. The polygonal areas are the cells, while the central dots -are the centrad continuations (nerve fibers) the flagella of the cells. ×920. -pp. <a href="#Page_63">63</a>, <a href="#Page_65">65</a>, <a href="#Page_66">66</a>.</p> - -<p><a href="#plate3">Fig. 26</a>. The flagella of the epithelium of a club are in this figure seen to extend -centrad, some beyond the nuclei. Cell outlines are not shown. ×920. pp. <a href="#Page_64">64</a>, <a href="#Page_65">65</a>, <a href="#Page_66">66</a>.</p> - -<p><a href="#plate3">Fig. 27</a>. The cells of the lower half of this figure belong to the ampulla, those of -the upper half to the canal of the peduncle. The right side of the figure is towards the -eyes (the ventral side) of the club. Globules of secretion are seen within the -ampulla cells, as also a globule without. The ring above the latter globule is -probably an empty shell of a floating cell. ×1320. pp. <a href="#Page_68">68</a>, <a href="#Page_69">69</a>, <a href="#Page_71">71</a>, <a href="#Page_73">73</a>.</p> - -<p><a href="#plate3">Fig. 28</a>. This figure is from a transverse section of a tentacle of Charybdea.<span class="pagenum"><a name="Page_84" id="Page_84">[84]</a></span> -The mass with darkly stained granules is the remains of a thread cell. The -ectoderm and a small part of the supporting lamella only are figured. Note the -large ganglion cell. ×920. pp. <a href="#Page_74">74</a>, <a href="#Page_75">75</a>.</p> - -<p><a href="#plate3">Fig. 29</a>. Part of a transverse section of a tentacle of Tripedalia. The endoderm -is not figured. The supporting lamella is seen to be considerably thinner than in -Charybdea. Note the subectodermal muscles, as also the muscle fibers to the thread -cells. ×920. pp. <a href="#Page_69">69</a>, <a href="#Page_74">74</a>, <a href="#Page_75">75</a>.</p> - -<p><a href="#plate3">Fig. 30</a>. This is a transverse section through the endothelium of a tentacle of -Charybdea in the line c d of <a href="#plate3">Fig. 32</a>. The dark lines bounding the polygonal areas -are the thickenings of the sides of the walls of the cells in the line indicated. The -central dots are the centrad continuations of the flagella. ×920. p. <a href="#Page_76">76</a>.</p> - -<p><a href="#plate3">Fig. 31</a>. This figure is a transverse section through a tentacle of Charybdea at -about the middle of <a href="#plate3">Fig. 32</a>, <i>i. e.</i> so near to where the tentacle joins the pedalium, -that the muscles within the lamella have all come to lie under the ectoderm. The -ectoderm is not shown. ×920. pp. <a href="#Page_75">75</a>, <a href="#Page_76">76</a>.</p> - -<p><a href="#plate3">Fig. 32</a>. A longitudinal section through the supporting lamella only, of a -tentacle of Charybdea, is here shown. In the upper part of the figure the muscle -fibers are seen wholly enclosed by the supporting lamella. In the middle of the figure -they are seen to pass out of their canal. In the lower part of the figure, the supporting -lamella is seen to bend to the right where it becomes continuous with the lamella -of the pedalium. ×920. p. <a href="#Page_75">75</a>.</p> - -<div class="figcenter bbox" id="plate1"> - -<p class="caption">CUBOMEDUSÆ. PLATE I.</p> - -<a href="images/plate1.jpg"><img src="images/plate1-sm.jpg" width="100" height="130" -alt="Plate 1 depicts Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11." /></a> - -<p class="caption">E. W. Berger, del.</p> - -</div> - -<div class="figcenter bbox" id="plate2"> - -<p class="caption">CUBOMEDUSÆ. PLATE II.</p> - -<a href="images/plate2.jpg"><img src="images/plate2-sm.jpg" width="100" height="130" -alt="Plate 2 depicts Figures 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 and 22." /></a> - -<p class="caption">E. W. Berger, del.</p> - -</div> - -<div class="figcenter bbox" id="plate3"> - -<p class="caption">CUBOMEDUSÆ. PLATE III.</p> - -<a href="images/plate3.jpg"><img src="images/plate3-sm.jpg" width="100" height="130" -alt="Plate 3 depicts Figures 23, 24, 25, 26, 27, 28, 29, 30, 31 and 32." /></a> - -<p class="caption">E. W. Berger, del. Heliotype Printing Co., Boston.</p> - -</div> - - - - - - - - -<pre> - - - - - -End of the Project Gutenberg EBook of Physiology and histology of the -Cubomedusæ, by Edward William Berger - -*** END OF THIS PROJECT GUTENBERG EBOOK CUBOMEDUSAE *** - -***** This file should be named 54276-h.htm or 54276-h.zip ***** -This and all associated files of various formats will be found in: - http://www.gutenberg.org/5/4/2/7/54276/ - -Produced by Donald Cummings, Bryan Ness and the Online -Distributed Proofreading Team at http://www.pgdp.net (This -file was produced from images generously made available -by The Internet Archive/American Libraries.) - - -Updated editions will replace the previous one--the old editions -will be renamed. - -Creating the works from public domain print editions means that no -one owns a United States copyright in these works, so the Foundation -(and you!) can copy and distribute it in the United States without -permission and without paying copyright royalties. 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