538 A. MILNES MARSHALL. 



one or other of which, or both, must therefore furnish the 

 physiological connection which the experiment proves to exist. 

 From the anatomical relations of the parts, and from the fact 

 that the proximal ends of the chiasma must almost certainly 

 have been injured in the operation, I think it probable that 

 the transverse commissure is the real connecting link in this 

 instance. As to the chiasma, the disposition of the fibres 

 suggests that it may be connected with the alternating move- 

 ments of the two arms of each pair which we have seen to 

 occur in the act of swimming. 



F. On the Functions of the Subepithelial Bands. 



The subepithelial bands are supposed by Ludwig, as we 

 have seen above, to constitute the sole or main nervous system 

 of Antedon. The experiments detailed above demonstrate 

 the incorrectness of this view. They show that the central 

 connection of the subepithelial bands on the oral disc is in no 

 way essential to, in fact, has nothing whatever to do with the 

 complicated and co-ordinated movements of swimming, and of 

 righting when inverted ; they show, further, that division or 

 destruction of the subepithelial band at any place does not 

 destroy or even disturb either the sensory or motor communi- 

 cations between the parts on either side of the injury. In fact, 

 they not only prove conclusively that these structures are not 

 the sole nervous system, but even raise doubts as to whether 

 they belong to the system at all. 



I think, however, that the close histological resemblance 

 between the subepithelial bands and the axial cords, coupled 

 with the close correspondence as regards their relations to the 

 ambulacral epithelium which exists betv/een Crinoids and 

 other Echinodermata in which, as in Asterids, they are most 

 certainly nervous, must compel us to consider these bands in 

 Antedon as nervous in- nature, though what their exact func- 

 tion is has yet to be determined. The ambulacral epithelium 

 is extremely and exceptionally sensitive, and irritation of it is 

 responded to in a definite and peculiar manner, i. e. by the 



