208 Dr. W. B. Carpenter on the 



themselves again, and again coiled up as before when the 

 irritation of the central organ was renewed. 



The only additional proof derivable from experiment as to 

 the nervous character of this apparatus, would be the produc- 

 tion of a similar effect in a single arm by irritating the supposed 

 nerve-cord in its course. But this, through the complete in- 

 clusion of the cord in the solid calcareous skeleton of the arm, 

 would scarcely be possible. 



As I distinctly remember mentioning this experiment to 

 Prof. Semper when I had the pleasure of a visit from him in 

 1868, I am rather surprised at his saying that no experimental 

 verification of the doctrine has been obtained. I was, on my 

 part, very glad to learn from him that the histological charac- 

 ter of the axial cords of Comatula closely corresponds with 

 that of what he felt assured to be the Nervous System of the 

 Holothurida, his admirable researches on which group ought 

 to be known to every comparative anatomist. 



Nothing but the engrossment of my spare time in the various 

 inquiries that have arisen out of the Deep-Sea researches which 

 I prosecuted in the vacations of 1868 and three following years, 

 has prevented me from publishing long before this the Second 

 part of my Memoir on Comatula, for which the essential 

 materials (in the shape of some hundreds of preparations, and 

 a series of most admirable drawings executed by Mr. George 

 West and Mr. A. Hollick) have been in my possession ever 

 since the appearance of the First. These drawings, made 

 from very careful dissections, show that the ovaries (or testes) 

 in the pinnules have exactly the same relation to the so-called 

 nerve-cord of Miiller, that the currants on a bunch have to 

 their stalk. I was led to trace this connexion, in the first 

 instance, by finding that the position of the ovary in the pin- 

 nule, between its two principal (afferent and efferent) canals, 

 exactly corresponds with that of Miiller's nerve-cord (r in 

 Prof. Semper's figure) between the two canals c.t and c.c of 

 the arm. They further show that in Comatula rosacea the 

 canal c.t, spoken of by Miiller as the tentacular canal, has no 

 connexion with the tentacles, and exists equally in the oral 

 pinnules which have no tentacles ; whilst the real tentacular 

 canal occupies the position x in Prof. Semper's figure*. This 



* That there is here, in Comatula rosacea, a most distinct canal, from 

 which the tubular tentacles originate, is a fact of which I am as certain 

 as I am of any point in the anatomy of this animal. Whether the same 

 may not be the case in Prof. Semper's Philippine Comatula, is a question 

 which I would commend to his careful investigation. I have a strong 

 belief that in a sufficiently thin section of a pinnule he would find his so- 

 called " fibrous cord " to possess a lumen ; though this may be obscured 

 by the collapse of the canal, which is not cylindrical but flattened. 



