292 ELEMENTARY BIOLOGY. [CHAP. 



c. The oviduct. Follow this down ; its first segment 

 already described (§ 2 c) is sometimes termed 

 the vagina. This opens by a tumid lip into a thin- 

 walled terminal segment, which enters the vesti- 

 bule side by side with the penis. 



d. The spermatheca or receptaculum seminis (receptacle 

 of the spermatophores) ; an elongated diverticulum 

 of the above-named terminal segment of the ovi- 

 duct, bound down during life to the hermaphrodite 

 duct (§ 2 b). Liberate it from this, and note that 

 it arises by a short neck which subdivides into 

 two coecal diverticula — a longer and stouter coiled 

 one, and a shorter one which terminates in a globular 

 enlargement (this lies, during life, tucked away in 

 the bend of the first coil of the intestine. Cf. 



§3B). 



e. The dart-sac ; an immense melon-shaped diverti- 

 culum of the base of the oviduct, in life backwardly 

 directed. Open it up and note its powerful muscular 

 walls ; lying within it will be seen 



f. the dart or spiculum amoris, a four-bladed calcareous 

 projectile. Its head overlies a papillate ingrowth 

 of the lining membrane of the sac. 



g. The accessory mucus or digitate glands; two 

 branching masses opening side by side into the 

 basal segment of the oviduct, immediately above e. 



H. The circulatory system. 



Examine an animal freshly removed from its shell, before 

 it is in any way dissected. The pulmonary vein will be seen 

 running in the wall of the lung-sac, in front of and in a line 

 with the excretory organ. Make an incision in this and 



