OF ANIMALCULES. 109 



at figures 110 and 111, in which may be seen the spiral 

 rows of dots : within it are also some hirger bodies, pro- 

 bably stomachs. The aperture of the mouth may be 

 discerned, and the currents it produces are indicated by 

 the arrows in figure HI. Length, l-240th of an inch. 



186. Cercaria j^l^Kfonecles {Eughna pleuronectes^Y,.) 

 The plaice-shaped Cercaria. — There are two varieties of 

 this species, mainly distinguished by their colour. The 

 first is green, very flat, and in form like a turbot or 

 plaice : as it can produce currents in the water, the 

 mouth must be furnished with cilia : its bright pink eye 

 is situated rather lower than in the C. viridis, and its 

 tail is abruptly attached to the body. In its interior 

 may be observed two or three large diaphanous bladder- 

 like bodies, which, as they vary in different specimens, are 

 probably stomachs : those sacs which have been filled 

 with colouring matter, are always apparently smaller, 

 but this food it appears to dislike, and endeavours to 

 avoid. Until, therefore, we can procure some coloured 

 substance better suited to its taste, the true form of the 

 alimentary organs cannot be demonstrated, although its 

 polygastric structure is almost certain. Like that class 

 of animalcules, it propagates by division : this I have ob- 

 served to commence longitudinally ; and when the two 

 heads are completed, and the eyes formed, the animalcule 

 has a very singular appearance, swimming about slowly 

 with a uniform motion, and enabling the observer to fol- 

 low it easily with the microscope. Ehrenberg supposes 

 it also to proceed from the egg, as he met with some very 



