OF ANIMALCULES. 113 



appearance is like the wheel animalcule, and on careful 

 examination cilia may be discerned : it is twice the size 

 of the C catelina. 



200. Cbrcaria vermicularis. The worm-like Cercaria, 

 — This is a long cylindrical animalcule, with a proboscis, 

 which it can extend or withdraw at pleasure. The body 

 has several conti'actions, dividing it into annuli, and the 

 tail is terminated by two bristles. It resembles the next 

 species. 



201. Cercaria forcipata {Distemma fore, E.) The 

 double-hooked Cercaria, — A sketch of this animalcule, 

 magnified, is shewn at figure 119. (See Book III.) 



