Bulletin of Museum of Comparative Zoology 17-2

BULLETIN OF THE MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD COLLEGE, IN CAMBRIDGE VOL XVII CAMBRIDGE, MASS., U.S.A 1888-1889 the original publisher Reprinted with the permission of KRAUS REPRINT CORPORATION New York 1967 Printed in U.S.A C O N T E NTS Page Xo — Studios On XX the Asterias X'o Newport — Laboratory Development of the Cah'areous Phites of W Fewkes (5 Thates.) July, 1888 J By — Ou from the Marine the Lateral By Holocephala S Canal System of the Selachia and Garman (5.3 Plates.) September, 57 1888 Xo — The Agassiz X'o man (13 Plates.) on By Julia — The of the Xo Coral Reefs of the PLawaiian — Studies Chick Xo tlie By A 121 April 1881) Primitive Axial Segmentation of the B Platt (2 Plates.) July, 1889 171 Morphology of the Carotids, based on a Study Blood-vessels of Chlamydoselachus By n Ayers — Cave Garman Tshuids (1 Plate.) Animals from Southwestern (2 Plates.) anguineus Gar- October, 1889 December, 1889 Missouri By 191 S 225 Xo — Studies from the Neivport Marine Zoological Laboratory Communicated hy Alexander Agassiz XX Oil the Beveloxunent of the Calcareous Plates of Asterias By J Walter Fewkes General Observations General Changes in External Form brought about by the Growth of the Calcareous Plates Development of Individual Plates, Eods, Pedicellariae, Spines, and Stone Canal Comparisons with other Asteroidea Comparison of the Plates of Asterias and Amphiura Summary Explanation of the Plates Asterias, the most development passes stellate form General Observations common genus This brachiolaria found in our nets of Asteroidea at Newport, in its tliroiigh a braehiolarian stage before in is it assumes a one of the most abundant larvse surface fishing at certain times of the yeai' Although the development of the brachioharia from the e^^ of the starfish has been accurately worked out, and the changes in the external form of the young Asterias, after it begins to assume a stellate form, have been well described by several naturalists, we are still ignorant of the mode and place of formation, and the sequence in the devel- opment, of some of the calcareous plates which help to give the stellate form to the young starfish after the absorption of tho brachiolaria ^Ve need more information as to how the ambulacral plates form, and when they appear, as compared with the dorsoccntral and terminals We not know how or when certain plates of the arm appear, and it is desirable to study the character of certain so-called embryonic plates reported to exist on the median line of the actinal side of the in the larva VOL XVTI — XO 1 arm BULLETIX OF THE Before we can arrive at any trustworthy conclusions as to the morphulo^y of the Echiuoderms, animals as varied in external foi'm as the Crinoids and Holothurians, it is necessary for us to Ivuow the character of the early ditfcrcnces in the calcareous plates, and tlieir sequence and of growth in the different groups Tliese plates are the struc- mode more than anv others, jrive the variety in external form to members of the Echinoderniata It may be confidently said that we know tlie general outlines of the growtli of the primary We plates of a representative Comatulid, Ophiuran, and Holothurian tures which, the diftei'ent know next nothing of the early formed plates of the Echinoids, to no subject which oifurs more interesting possibilities of than this Little is known of the mode of growth of certain discovery of the plates of the body and arms in tliose Asterids which have a and there is nomadic brachiolaria.* The following paper, therefore, is offered as a contrilmtion to the recorded observations on the growth of the plates in the starfish The common species of Asterias found at Newport resembles closely Asteracanthio)i beri/liniis of A Agassiz, and has close alfinities with Asterias viih/aris, to be the same tSL, and A Forbes'd, Desoi'.f as herylhms, there are some which would lead one to regard them as of starfishes found tures of both ,1 by me vttlyaris * Our knowledge of Although I suppose it peculiarities of coloration X diti'erent While the species Newport, in the adult condition, have feaand A Forbesil, it is not possible for me to at growth of tlie plates whicli form the mouth parts of and unsatisfactory t Tlie genus Leptasterias is thought to be sufBcicntly well separated from Asterias by the character of its development to merit a new name, as shown by the staitish is tlie fragineiitary Prof Verrill The both Astrracauthion palluhis, Agass., and AatcraAgass., have a bluish tint, while the males have a reddish color, according to A Agassiz indicates that there is a difference in color in the female starfishes which we studied The color of the females of the species of t cant/lion starfish fact that all females of hcrtjlinus, which I tried to fertilize was different from those of the species of Astera- canthion used by A Agassiz in tlie artificial imjjregnation of the starfish 3Iany specimens of female starfishes, which had ripe ova, have a chocolate-brown color, and a bright orange madreporic body Starfishes of this color were the only ones which cast their eggs, although I had in the aquaria bright red and bluish colored starfishes of all sizes In A Agassiz's specimens those with a bluish tint are invariably females, while the reddish brown or reddish are males I not know the color of our male Newport Asterias, but several specimens of the reddish brown s[)ecimens laid eggs in great numbers on «everal occasions Ova nearly mature were also cut out of specimens of tiiis color MUSEUM OF COMPARATIVE ZOOLOGY my brachiolariae are the young As most forms were raised from brachiolarias captured almost impossible to say definitely to which determine of which of these of the stellate younger by surface tishmg, it is I was not able to fertilize artificially species of Asterias they belong The Asterias, although plenty of ripe ova were repeatedly found difficulty seemed to be in all cases in procuring the males The following mention of their time of ovulation may be of assistance to those who have in mind a visit to the New England coast for the study of Echinoderm embryology The eggs of Ophiopholis were July 17th The young of -4 Maine, on found at Newport, R L, in fertilized at Eastport, squamata w^ere July, August, and September Echinarachnius can be artificially fertilized at Newport in August and September The probable time of ovulation is the end of August and the first weeks of September Plutei are abundant iu September A specimen of Arbacia laid eggs at Newport iu August I have found the majority of the plutei of Arbacia in July Large numbers of Leptasterias with attached young were taken in Massachusetts Bay in April Multitudes of a red pupa of some Holothurian were collected at Provincetown in April The pupee of Synapta are found sporadic at Newport in August and September by surface found iu July fishing The auricularice of Synapta are The material which has served for the following observations on the starfish young was collected iu two ways The younger forms in some instances were raised from the brachiolari?e, collected by surface This material includes all stages from of the appearance plates, or calcai'eous skeleton, up to the starfish with three pairs of ambulacral rafters The remaining fishing with the Miiller net the first young specimens, from the young Asterias with three pairs of ambulacrals into the oldest stages figured, were found on the under side of stones near low-tide mark The large stones near the outer landing-place at the Laboratory were turned over, and the young starfishes were found This method of collecting involves continued search, clinging to them as Asterias is not common in the immediate neighborhood of the Laboratory The method by which the preparations of starfishes described in this paper were made is as follows The young starfishes were killed in alcohol (.35%) They were then (50%, 70%, 90%) rapidly passed through different grades to absolute alcohol They were then clarified in BULLETIN OF THE clove oil, and mounted from in balsam Those which were stained were alcohol into Grenacher's alcoholic borax-carmine, 70% washed, afterwards placed in from 90% to 100% alcohol, then removed The preparations mounted without staining to clove oil and balsam carried show very well the relation of the plates to each other, but it is necessary to use a staining fluid to bring out the tissues of the organs in the immediate vicinity of the calcareous skeleton In the study of the plates on the abactinal side of the disk of older it was necessary to separate the arms from the disk proper specimens, No dissection was resorted to in this separation, for the arms are easily broken from the disk along the suture between the first dorsal plate and the second dorsal radial, leaving the former, as well as the genitals and all central intermediate plates between them, on the disk with the dorsoIn older stages staining fluid was used, but the best results, as far as the plates are concerned, were obtained in specimens artificial staining The use was resorted of chloroform, where no to which gave good results in Amphiura,* was not resorted to in Asterias General Changes in External Form brought about by the Growth of the Calcareous Plates By the growth of the calcifications in the growing Asterias the animal stellate outline, passing into this form from a spherical or dis- assumes a coid larva These changes are almost wholly the result of change in form or modification in the an-angement of the plates, but the peripheral appendages, spines, pedicellarise, and spicules also play an important part in this growth When the growth of the primary plates begins, the is not stellate in form, and all the starfish young early plates are confined to the body The elongation of the arms are the most prominent results of the modification in the shape of plates, of addition to those In the growth of already existing, and of enlargement of the same the arm no marked symmetry in the formation of plates on the actinal and abactinal regions of the arm was noticed There is also no symin the gi'owth of the calcifications in the actinal and abactinal regions of the body It is not in the province of this paper to give more of the development of Asterias than is necessary to understand the relation of the metry observed * this I tried reagent a few specimens of tlie young Amphiura with clove clarifies them better than chloroform oil, and find that MUSEUM OF COMPARATIVE ZOOLOGY plates to one another, and to aid in their identifications and homologies consideration of the internal organs is a most interesting and neces- A sary chapter in a study of the growth of the stellate form of the starfish, Some idea but it is one of which little is written in the present paper of the origin of organs in immediate connection with the plates is necessary, however, to understand the homologies of the calcareous formations with which this paper is specially concerned The development of the brachiolaria of our common Asterias is well known through the researches of A Agassiz,* and is not here considered account opens with a late stage of the brachiolaria, in which certain calcareous nodules, described in the paper mentioned, have already appeared, and in which the form of a stellate animal is obscurely marked My out It is intended first to follow the general course of plates collectively, and plates will be taken later in the paper, the up one In the starfish body, as growth of these development of individual after the other is well known, there are two regions, called the actinal and abactinal, the lower and upper, ventral and dorsal, which may be studied The primary plates in these two hemisomes differ No plate from the very first in number, arrangement, and distribution is ever formed in the centre of the actinal hemisome comparable with that in the middle of the abactinal, and it would be a task which the author is not called upon to undertake to compare the ten ambulacrals five terminals and five genitals formed on the lower hemisome with the of the abactinal region of the body In the early condition of the plates there is an indication of the disk- it is somewhat masked we look at the lower or anal pole of the brachiolaria (PI I fig 1) laterally, and in such a way that the forming plates are on the side turned to the observer, we can see ten small calcifications, an'anged in two U-shaped lines, one within the other If we so place the brachio- like form which the young Asterias has, but If laria that the anal pole is below, or pointing to the lower side of the the madreporic body on the left hand of the observer and the anus of the brachiolaria on his right, we notice the five plates, now in figure, * A On the rubens, VI., 1863 M Embryology of Asteracanthion heryUrais, Ag., and a Species allied to Ag Proc Aiuei' Acad Arts and Sci., T., Asteracanthion pallidus, Also separate, 1863 of the Starfisli, published in December, 1864, advance Pt I., Vol The same, reprinted with descripS., of L Agrassiz tions of the hard parts (calcareous skeleton) of several genera and species of " Asteroidea, under the title, North American Starfishes," Mem Museum Conip Embryology v., Contrib Nat Hist, of U Zoology, v., No 9, 1877 — BULLETIN OF THE the form of calcareous spicules, t^-t^, of the larger U, begiuning with one, t^, just south of the madi-eporic opening; followed by a second, ^^, a little east of south of the first ; a third, t^, north of east of the second ; a fourth, of the t\ east of north of the third ; and a With these alternate the rods first fifth, t^, about due east of the smaller U, the first, g\ being placed about east of the madreporic opening, the second, r^-, third, g^, fourth, g*, and fifth, g^, alternating respectively with the 1st -2d, 2d -3d, 3d - 4th, 4th - of the larger U Between the first 5th, of the larger are the terminals genital and the between other consecutive plates, ; fifth is U the genitals.* a broader space than the open part of the larger terminal which The members U those of the smaller lies an unclosed region which forms the brachiolarian notch As the brachiolaria is slowly absorbed, this notch is more and more reduced U It is in extent, until Us become it is almost wholly lost, when by this reduction the rings forming the abactinal calcai'eous surface of the two young starfish If now we rotate the brachiolaria on its axis, through a right angle, body faces the observer, the anal pole being so that the madreporic still below, we have the following perspective of the two Us It then be seen that the larger and the smaller Us not lie in one and the same plane, but that the formed by the terminals is situated will U on a greater than that of the genitals This fact explains why it is that the figure formed by the line of the latter is smaller than that of the former It is as if the U of the terminals was placed on the circle great circle of a hemisphere, smaller The while that difference in size of the two of the letters follows genitals (U) is a due to the spherical form of the walls of the stomach of the brachiolaria It is somewhat difficult to understand the exact relationship between the dorsal and ventral or abactinal and actinal f surfaces of the young starfishes, and the relation of the plates which form in these two regions These two surfaces are separated by the stomach of the brachiolaria, and are not at first parallel, but form an acute angle with each other ; and if the plane in which the plates of the abactinal hemisome were continued to meet that of the primitive extensions of the water tubes, they would cut each other at a small angle A Agassiz described them as two "warped spirals," and if in early stages lines be drawn, connecting the terminal and genital plates, the planes in which they * The term t " "