376 Dr. Carpenter on the Structure, Physiology, [June 15, 



in other striated muscle, and that its excessive tenuity is probably the cause 

 of its escaping observation. 



XVI. "Researches on the Structure, Physiology, and Development of 

 Antedon (Comatula, Lamk.) rosaceus.'' By Dr. W. B. CAR- 

 PENTER, F.R.S. Received June 15, 1865. 

 (Abstract). 



The author, after adverting to the special interest attaching to the study 

 of this typical form, as the only one readily accessible for the elucidation of 

 the life-history of the CRINOIDEA, states it to be his object to give as com- 

 plete an account as his prolonged study of it enables him to offer, of its 

 minute structure, living actions, and developmental history, taking up the 

 last at the point to which it has been brought in the memoir of Prof. 

 Wyville Thomson. 



He prefaces his memoir with an historical summary of the progress of our 

 knowledge of the distinctive peculiarities of this genus, and of its relation 

 to the Crinoidea; and he shows that the first recognition of this relation- 

 ship was most distinctly made by Llhuyd, at the beginning of the last 

 century, though that recognition has been passed without notice by most 

 subsequent writers, and is altogether ignored by MM. de Koninck and 

 le Hon in their recent history. 



The author then proceeds to describe the external characters of Antedon 

 rosaceus ; and shows, from its habits as observed in a vivarium, that al- 

 though possessed of locomotive power, it makes so little use of this under 

 ordinary circumstances, that its life in the adult condition, no less than in 

 its earlier stage, is essentially that of a pedunculate Crinoid. 



He then gives a minute description of the several pieces of the skeleton 

 the accounts of these previously given by J. S. Miller and Prof. Job. 

 Miiller not being in sufficient detail to serve as standards of comparison to 

 which the parts of fossil Crinoids may be referred. And he directs special 

 attention to the curiously inflected rosette-like plate, previously unnoticed, 

 which occupies the central space left within the annulus formed by the 

 adhesion of the first radials. This plate is in special relation to the organ 

 termed by Joh. Miiller the " heart," but certainly having no proper claim 

 to that designation, being a quinquepartite cavity in the central axis, from 

 the walls of which there pass out not vessels but solid cords of sarcode, 

 into the rays and arms, and also into the dorsal cirri. The inflexions of 

 the rosette-like plate serve for the support and protection of the large cords 

 passing into the rays, each of which has a double origin, and a connexion 

 with the adjacent radiating cords that reminds the anatomist of the 

 " circle of Willis." 



The skeleton of the adult differs so widely in the forms and relations of 

 its parts from that of the early Pentacrinoid larva described by Prof. 

 Wyville Thomson, that the derivation of the former from the latter can 

 only be understood by observation of all the intermediate stages. When 



