Fio. 123. 



Nervous system of 3 Streptoneurous Gastropods, showing the dialyneury and zygoneury. 

 dorsal aspect. A, Paludina (after Bouvier, somewhat modified); B, Triton (after Haller) ; C, 

 Lamellaria (after Bouvier). a6.gr, abdominal ganglion ; br.n, branchial nerve ; ce,g, cerebral 

 ganglion ; c.pe, cerebro-pedal connective ; c.pl, cerebro-pleural connective ; di', di", left and 

 right dialyneury; i.i.g, infra-intestinal ganglion ; ot, otocyst; pa.n, pallial nerve; pe.g, pedal 

 ganglion ; pl.g, pleural ganglion ; pl.pe, pleuro-pedal connective ; s.i.g, supra-intestinal ganglion ; 

 st.g, stoniato-gastric ganglion ; ri.c, visceral commissure ; vi.cf, vi.c", supra-intestinal and infra- 

 intestinal part of the visceral commissure ; zy', zy", left and right zygoneury. 



143 



