NERVOUS SYSTEM OF ANTEDON ROSAOEUS. 547 



calcareous test offer us a condition of things in some respects 

 approaching that of the Crinoid. 



Concerning the morphology of the central capsule, I feel in 

 much more doubt. Dr.Carpenter^s observations lead to the belief 

 that, at any rate inits present form, it isconnected with the change 

 from the pedunculate to the free-swimming condition ; and it 

 is worthy of notice that the two actions with which it has been 

 found to be specially concerned physiologically, i. e. the move- 

 ments of swimming and of righting, are ones that the 

 pedunculate form, from the very nature of things, can never 

 exercise. 



While, however, this theory of the derivation of the system 

 of the central capsule and axial cords of a Crinoid by concen- 

 tration from the antambulacral portion of a continuous nerve- 

 sheath render a comparison between the Crinoids and the other 

 Echinoderms possible, it still leaves the gap between the two 

 groups a very wide one. Crinoids are sometimes compared 

 with Asterids or Ophiurids, but they differ from both these 

 groups in a great number of points of fundamental importance. 

 In the absence of any representatives of ambulacral ossicles, 

 the convoluted character of the alimentary canal, the position 

 of the anus, the permanent communication between the ambu- 

 lacral system and the coelom, the replacement (functionally if 

 not morphologically) of the madreporic plate by a number of 

 ciliated openings, we have, quite apart from the entirely excep- 

 tional features of the nervous system, a list of characters, which 

 could very easily be added to, which mark off the Crinoids as 

 a group widely separate from the other Echinoderms. 



When we bear in mind that in a number of these points the 

 Crinoid condition is not only not a primitive one, but a very 

 highly specialised one, the gap becomes wider still. 



I do not propose at present to pursue further this point, 

 which has recently been noticed by both the Carpenters, 

 and will close my paper by venturing to call attention to 

 the great importance of supplementing morphological and 

 histological inquiries by direct experimental investigations. In 

 this age of specialisation there is a very real danger of men 



