BUSYCON. 135 



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 nidamental 

 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 hypohranchial 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, osphradium, 

 hypobranchial gland (cut in opening the mantle cavity), and, if 

 the specimen is a female, the nidamental gland. The open- 

 ing 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 a little to the right 

 and anterior to the anus. If possible, insert a guarded bristle 

 into this opening and see what becomes of it. Trace the oviduct 

 from the ovary along the columellar side of the liver. See what 

 becomes of it. Examine the inside of the nidamental gland 

 and see its relation to the oviduct. 



If the specimen is a male, follow the vas deferens from the 

 testis to the base of the penis. 



Circulatory System. — Remove the thin membrane that forms 

 the roof of the pericardial chamber. 



1. The heart consists of : (a) the large, rounded ventricle; 

 (b) the smaller, conical, thin-walled auricle. 



2. The auricle receives blood by two vessels. One, return- 

 ing blood from the gill, runs along the left side of the gill to its 



