GENERAL PART. 59 



VII. GENERAL PART. 



The researches on the embryonal and postembryonal development of 

 no less than 6 new types of Comatulids put forth above enable us to form a 

 better judgment of the general value of the results obtained from the pre- 

 vious studies in the embryology of Crinoids, these having been based solely 

 upon one type, viz, the genus Antedon s. str. ; even though three different 

 species of this genus have been the object of these studies (namely, mediter- 

 ranca Lamarck, adriatica A. H. Clark, and bifida Pennant) they are so closely 

 related that they could hardly be expected to differ essentially in their devel- 

 opment. Our previous knowledge accordingly rests only on one single type, 

 and it is then of some value to have the results reached from that one type 

 tested by researches upon other types. As might be expected, some of the 

 results previously regarded as holding for the Crinoids as a whole are now 

 seen to apply only to Antedon, but upon the whole the differences are not 

 great, the Comatulids apparently being a very uniform group as regards 

 embryology, in accordance with the fact that, in spite of the great number 

 of genera and families established, this whole group corresponds at most to 

 only a single family of the Crinoids. As A. H. Clark justly says (Monograph 

 of the Existing Crinoids, p. 18), we have here "the curious anomaly of a 

 group which, considered from one point of view is a true class, but considered 

 from another point of view does not even rise to the dignity of a subfamily." 36 

 Greater deviation from the Comatulid type of development may be expected 

 among the stalked Crinoids, but about this nothing is known as yet. 



It is not the intention to enter here on a discussion of the greater ques- 

 tions of Echinoderm morphology and phylogeny. That may be postponed 

 until all the material for the study of Echinoderm development collected 

 by the author has been worked out; and, upon the whole, discussion of these 

 intricate problems may not suffer by waiting for the accumulation of more 

 facts in the ontogeny of the Echinoderms. 



I. DEPOSITION OF THE EGGS. 



In Antedon the eggs are retained in clusters around the genital openings 

 (inclosed in the egg-membrane) until the embryos have developed the ciliated 

 rings and the development has been carried so far that the embryo, almost 

 immediately after the rupture of the egg-membrane, is ready to attach itself 



30 1 may also quote from A. H. Clark's "Crinoiden der Antarktis" (Deutsche Siidpolar-Exped. xvi, 

 Zool, Bd. vm, 1915, p. 110) the following passage, with which I agree fully: "Daher sind die Comatuliden, 

 rein als integrierendes Element der heutigen marinen Fauna betrachtet, das genaue Equivalent der Aster- 

 oidcn, Ophiuriden, Echiniden und Holothurien, wahrend sie phylogenetisch nur cine Abteilung der Pentac- 

 rinitiden bilden. Daher wird es notwendig, die anscheinend unlogische Einteilung der Comatuliden in 

 Unterordnungen, Familien Subfamilien u. s. w. anzunehmen, wobei man im Auge behalten muss, dass die 

 ganze ungeheure Reihe von Arten systematisch das Equivalent der 9 bekannten Genera der Pentacrin- 

 itiden ist, . . . und dass zusammen mit diesen 9 Gattungen und Thiolliericrinus die Comatuliden mit 

 Hinsicht auf die phylogenetische Folge der Crinoidentypen nur eine einzige Familie bilden." 



