PLAN OF DEVELOPMENT OF ECHINODERMS. 79 



which I have had frequent occasion to examine, have satisfied rne that 

 the process of development is the same, with the exception that it is 

 shorter. The hnrvae of Ophiurans examined hy Professor Agassiz at 

 Charleston would lead to the same conclusion with reference to the 

 Ophiurans; while, from the drawings of Midler, it is easy to satisfy one's 

 self, with the above data, that the two types of development of IIolo- 

 thurians examined by him are only modifications of each other. As the 

 only larvae of Ilolothurians which I have seen belong to the " Wurm- 

 formiger" type, I am unable to state this from actual observation. It is 

 evident that we have also in Comatula these two types of development. 

 Professor Agassiz frequently observed that in a species of Comatula found 

 in Charleston, S. C, the young embryos remain attached to the par- 

 ents ; while Thomson and Busch have found the larva) swimming freely 

 about. 



[An important paper on the development of Comatula by Goette, in 

 the Archiv fiir Microscopische Anatomic for April, 1876, gives us the 

 early stages of its embryo. Goette shows conclusively that the type of 

 the crinoidal development is echinodermoid. We have, as in Echini, 

 Starfishes, Ophiurans, and Holothurians, an original digestive cavity, from 

 which arises the water-system, as diverticula. This observation is in 

 direct contradiction to that of MetschnikofF, who distinguishes the Cri- 

 noids from the other Echinoderms by the absence of these processes. 

 Goette's observations of the early stages are, however, in complete agree- 

 ment with the usual mode of development among Echinoderms. Unfortu- 

 nately the subsequent stages are all figured from embryos preserved in 

 osmic or chromic acid, and while I have the greatest respect for Goette's 

 technical skill, the very fact that in so many general points he differs, 

 both from MetschnikofF and myself, throws considerable uncertainty on 

 the whole of his memoir. He begins by stating that the larval mouth 

 (the subsequent anus of the other Echinoderms) is entirely obliterated. As 

 he has not followed this from living embryos, we must be pardoned if, 

 knowing, as we do, the difficulty of tracing the gradual changes in 

 living embryos of the most transparent kind, we doubt many of his 

 conclusions obtained from the study of opaque embryos acted upon by re- 

 agents. Although Goette has derived his knowledge of the present paper 

 from the excellent abstract in Leuckart's Jahresbericht, he has not only 

 credited me with a very indifferent treatment of the embryology of 



