Microscopical Essays. 553 



well as the colour, it differs confiderably from it. It fometimes 

 contracts the head and tail, fo as to form a fpherical figure ; at 

 others the fides project outwards. Is found in the fpring, in 

 ditches of Handing water. 



131. Cercaria Seiifera. 



Cercaria cylindracea, antice anguPdor, poflice acuminata. 

 Cylindric cercaria, the fore-part fmalleft, the hind-part pointed. 



This is a fmall cercaria, the body rather opake, round, the 

 upper part bright, .and fmall er than the reit ; the trunk is 

 more opake, the tail fharp, near it is a little row of fhort hairs. 

 It has a flow rotatory motion, and is feldom to be met with, and 

 when found it is in fait water. 



132. Cercaria Hirta. 



Cercaria cylindrica, antice fubtruncata, poPcice obtufa, bimu- 

 cronata. Cylindrical cercaria, the fore-part foinewhat truncated, 

 the lower part obtufe, fmifhing with two fmall points. 



A cylindrical opake animalculum, with two fmall points at 

 the lower end, moveable, yet rigid, and placed at fome diftance 

 from each other ; when in motion, the body feems as if it was 

 furrounded with rows of fmall hairs, feparated a little from each 

 other. It was obferved in fait water. 



133, Cer- 



