1876.] On the Development of Antedon rosaceus. 211 



IV.. "On the Structure, Physiology, and Development of Ante- 

 don (Comatula, Lamk.) rosaceus." By William B. Car- 

 penter, M.D., F.R.S. Received December 16, 1875. 



[Plates 8, 9.] 



When, in 1865, 1 communicated to the Royal Society the First Part oi 

 a Monograph on the Anatomy, Physiology, and Development (excluding 

 the earliest stages previously described by Prof. Wyville Thomson) of an 

 animal which might be regarded — except in certain comparatively unim- 

 portant particulars — as a type-form of the whole Crinoidal series, I had 

 so nearly concluded my investigation of the subject of it, that I fully 

 contemplated the presentation of the Second and concluding part in the 

 course of a year or two. Uncertain health, however, interfered with its 

 completion in the first instance ; and my spare time has since then been 

 so far taken up by the various inquiries that have arisen out of the Deep- 

 Sea researches which I prosecuted in the vacations of 1868 and three 

 following years, that I have found myself quite unable to resume the 

 study of Antedon. Thus it comes to pass that, though I have now had 

 by me for a period of ten years the results of my previous labours, as 

 presented in several hundred preparations, with a series of most admirable 

 drawings executed by Messrs. George West and A. Hollick, illustrating 

 almost every point of primary importance not only in its structure, but also 

 in the history of its development from nearly the earliest Pentacrinoid 

 stage, all this material has remained unpublished ; for I have felt that the 

 completion of my Monograph in a manner worthy of its subject required 

 that certain obscurities should be dissipated and certain gaps filled up ; 

 and it now, also, becomes desirable that the Histology of this type should 

 be more fully elucidated by the aid of modern appliances, and that the 

 earliest phases of its Development should be thoroughly reinvestigated. 

 I especially desire to ascertain whether the free-swimming larva (or 

 pseudembryo) has a Gastrcea stage, and to follow out the derivation of 

 the gastric and perivisceral cavities of the Pentacrinoid, and of its original 

 tentacular system, from the structures of the pseudembryo — points on 

 which Prof. Wyville Thomson's Memoir, admirable as it is, does not 

 enlighten us. This stage of the history has been subsequently studied 

 by a most able observer, Herr Metschnikoff * ; and the conclusions he 

 has arrived at in regard to the origin of the tentacular system I find 

 to be essentially accordant with those which I had drawn from my own 

 researches on a later stage. 



In the autumn of the year 1868 I had the pleasure of a visit from 

 Dr. Semper, who had then newly returned from a long residence in the 

 Philippine Islands, where he had not only made a large collection of 

 different species of Antedon (including many new ones of singular con- 



* Bulletins de l'Acad. Imper. de St. Petersb. 1870, pp. 508, 509. 



