TREMATODE SPOROCYSTS AND CERCARI^. 201 



teased and examined with the aid of the compound microscope. 

 No sporocysts were seen in place. Sporocysts were found on the 

 bottom of the dish in which the snails that had been removed 

 from their shells were lying, also in the dish which held the snails 

 still in the broken shells. It would appear that the sporocysts 



Fig. 3. Cercaria in sea water, ventral view, showing excretory vessels in front 

 of ventral sucker, rudiments of testes, etc. Length 0.25 millimeter. From 



Ilyanassa ohsoleta. 



are rather loosely lodged in the mantle cavity, since they make 

 their appearance when the broken shells and partly exposed ani- 

 mals are shaken about in the water. Some 600 sporocysts were 

 obtained from this lot in a short time in this way. When the 

 snails were picked to pieces, washed, and the water decanted, an 

 increased number of sporocysts were obtained. The number of 

 cercarise in these sporocysts was greater than that recorded in the 



