ON THE NEUVODS SYSTEM IN PELECYPODA. 



43 



In summing up, Drew concludes, in general terms, that ' " it seems 

 more likely that the nervous systems of all molluscs have been derived 

 from some such generalised a type as found in Chiton, and that each class 

 has developed ganglia accoi'ding to its needs, than that the ancestors 

 of the Lamellibranclis possessed the comparatively complex system of 

 ganglia found in Gastropods." 



Fig. I.— Model of uervous system of Kucula intclctis, seen from the veutral aspect. 

 c.G. cerebral ganglion; p.g. pedal ganglion; v.g. visceral ganglion. 



During the last few years I have examined minutely several 

 specimens of Nucula nucleus, and amongst other things have made 

 a careful study of the nervous system by means of transverse and 

 horizontal sections and by reconstruction after the Born (or rather 

 Newton -) method. Upon the general conformation of this nervous 



' Drew, I.e., p. 373. 



- Newton, "On the Brain of the Cockroach": Quart. Journ. Micro. Sci., vol. xix 

 (1879), p. 341. 



