226 ZOOLOOT. 



The ovaries or testes, as the sex of the clam may be, are 

 bilaterally symmetrical, blended with the wall of the risce- 

 ral or liver-mass, and are yellowish. The genital openings 



Fig. 159. — Nervous system of the clam, natural size, a, cesophageal ganglion ; fi, 

 commlBsnre anterior to the mouth ; c, pedal commissure ; d, pedal ^nglia ; c, parieto- 

 Bplanchnic commissures ; /, parieto-splanchnic ganglia ; g^ branchial nerves ; A, I, pal- 

 iial nerves ; i, siphonal nerves ; k, aual nerves ; m^ nerves to the anterior adductor. — 

 Drawn by W. K. Brooks. 



are paired and lie near the base of the foot. Both eggs and 

 semen arise from the epithelium of the sexual glands. The 

 eggs pass out into the body-cavity, or accumulate between the 



