COMPARATIVE ANATOMY 



Fig. 1 8 



Nervous system of Helix aspersa, an example of the euthyneurous condition in 

 which the pleural, visceral, abdominal and pedal ganglia are fused to form a 

 subcesophageal ganglion mass. B. Nervous system of Limn^ea, an example of 

 the short-looped euthyneurous condition in which the ganglia are separate 

 (after de Lacaze Duthiers). C. Nervous system of Paludina vtvipara, an 

 example of the streptoneurous condition, a&d^ abdominal ganglion; bucc^ 

 buccal ganglia; c^r, cerebral ganglia; c^c, cerebro-pedal connective; cue, 

 cerebro-pleural connective; gd^ conjoined genital duct; «/J facial nerve; 

 ^gt genital nerve ; nle, exterior labial nerve ; nli, internal labial nerve ; 

 nop, optic nerve ; np, pedal nerves ; «//, left pallial nerve ; «/;«, median 

 pallial nerve; 7ipn, pental nerve; npr, right pallial nerve; o, osphradium ; 

 <3ir, oesophagus ; oic, otocyst ; ped, pedal ganglion; ph, pharynx; //, pleural 

 ganglion ; rs, radula-sac ; sbg, suboesophageal ganglion mass ; sb, sub-intestinal 

 ganglion ; sp, supra-intestinal ganglion ; vis, visceral ganglion ; vn, visceral 



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