226 



ZOOLOGY. 



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

 bilaterally symmetrical, blended with the wall of the visce- 

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



Pig. 159-— Netvons system of the clam, natnral size, a, cesophageal ganglion ; i, 

 commissTiTe anterior to the moath ; e, pedal commissure ; d. pedal ganglia , «, parieto- 

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

 lia) nerves ; i, siphonal nerves ; ik, aual nerves ; m, nerves to the anterior addnctor.— 

 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 



