55 2 



Microscopical Essays. 



i 29. Cercaria Poduria. Fig. 37 and 38, Plate XXV, 



Cercaria cylindracea, poflice acuminata fubfifla. Cyli : 

 cercaria. the hind-part (harp, and fomewhat cloven. 



It refembles the young ones of the podura which live among 

 the lemna, is pellucid, and feeras to confift of a head, a trunk, 

 and a tail ; the fore-part refembles the head of a herring, the trunk 

 is cyhndriCj and replete with black fpiral interlines ; appears 

 more oriels ventricofe, at the will of the animal. Nothing to be 

 difcovered in the hinder-part. The tail, in moft fit nations, ap- 

 pears divided into two brill les. When the animal moves, there 

 is a continual motion among the interlines, which, from the 

 various (hades they occaflon, make the body appear very rough ; 

 fome lateral hairs '(cilia) are fometimes perceived. It moves from 

 one place to another, turning round at the fame time as upon an 

 axis. It is to be found in November and December, in marfhy 

 places that are covered with lemna. Fig. 36, a the head, b the 

 trunk, c the tail, d with one point, it is feen at e, Fig. 37, with 

 two points ; f the hairs on the fide. 



130. Cercaria Viridis. 



Cercaria cylindracea mutabilis, poflice acuminata fiffa. Cylin- 

 drical cercaria, mutable, the lower end (harp, and divided into 

 two parts. 



This animalculum, when in it's longed (late, is not unlike the 

 preceding ; but from the changes to which the body is fubjecl, as 



well 



