1 3 ° 
cover the whole of the surface of the spermatheca. 
The spermatozoa have a narrow, slightly-curved head 
and a long tail. The duct of the spermatheca is 
narrow and thick-walled, and contains muscular fibres. 
Certain large cells lie in connexion with the duct 
externally. The mucus gland contains cells filled 
with secretion. 
