TYPE MOLLUSCA. 



Jill 



while another pair pass to a pair of ganglia lying below the 

 radula and in intimate connection with a peculiar subradular 

 organ, probably sensory, lying in this region. 



FIG. 130. DIAGKAM OF NERVOUS AND EXCRETORY SYSTEMS OP Ghiton siculus 



(combination of two figures by HALLER). 



no = nephridial orifice. 



an auus. 



Br = cteuidia. 

 go = genital orifice. 

 n = nephridiuin. 



oe = oesophagus. 



pe = pedal nerve cord. 



pi = pleural nerve-cord. 



As regards sense-organs, in addition to this subradular 

 organ whose function is entirely problematical, ridges of 

 sensory epithelium exist along the sides of the body in the 

 mantle-cavity. One such ridge runs along the inner wall of 

 the mantle-fold, while the other is found at the bottom of 

 the mantle-cavity passing over the bases of the branchial 

 plumes and sending a short prolongation outwards upon each 

 of these structures and seeming thus to correspond with the 

 osphradia of other Mollusca. 



