146 MOLLUSCA 



15. The gonad, which is borne on the dorsal surface of the 

 liver, and differs in individuals from red and brown to yellow. 



16. The stomach, which lies on the left (external) surface 

 of the liver. It is curved and light colored and is frequently 

 rather indistinct. 



17. The kidney, which lies on the dorsal surface, and a 

 little to the left side, on the anterior end of the liver. It is 

 somewhat rectangular in shape and differs in color from a 

 yellowish brown to a chocolate color. The kidney is com- 

 posed of two parts, the large acinous portion, and the smaller 

 tubuliferous portion. The latter lies along the left side of 

 the former, by the side of the pericardium. 



18. The pericardium lies to the left of the anterior end of 

 the kidney. Through its dorsal wall the yellowish heart can 

 generally be seen. 



19. The columellar muscle, which attached the animal to 

 its shell and enabled it to withdraw, can be traced to the foot. 



20. If the specimen being examined is a female, the large 

 yellowish nidamental gland will be seen near the right side. 



21. The large, brownish gill lies to the left of the nida- 

 mental gland in the female and anterior to the heart. 



22. The osphradium is a small, brownish organ to the left 

 of the anterior end of the gill and at the base of the siphon. 



23. The hypobranchial gland is a glandular portion of the 

 mantle, to the right of the gill (between the gill and the nida- 

 mental gland, in the female). 



Make a drawing of the animal as a whole, showing as 

 many of the observed points as possible. 



Open the mantle chamber by cutting the mantle along 

 the right side of the gill to the limit of the cavity, reflect the 

 flaps, and notice the position and structure of the gill, osphra- 

 dium, hypobranchial gland (cut in opening the mantle 

 cavity), and, if the specimen is a female, the nidamental 

 gland. The opening of the rectum will be seen at the end of 

 a short papilla in the right side of the mantle cavity. The 

 opening of the nidamental gland will be seen on an elevation 



