55 6 



Microscopical Essays. 



minating in two pellucid thorns ; fome times a fwelling is per- 

 ceived between thefe. It often proje&s from the in ci lion at the 

 apex, a kind of cloven probofcis. Is found in water where there 

 is duck-weed, d d the points of the fore-part, e the probofcis. 



138. Cercaria Forcipata. 



Cercana cylindrica, rugofa, probofcide forcipata exfertili, 

 cauda bicufpidata. 



Cercaria cylindrical, wrinkled, with a forked probofcis, that it 

 can thru ft out, or pull in. It is found in marfhy fituations. 



139. Cercaria Pleuroneaes. Fig. 38, Plate XXV. 



Cercaria orbicularis, cauda unifeta. Orbicular the tail, confid- 

 ing of one brittle. 



It is membranaceous, rather round, and white. In the fore- 

 part are two blackifh points. The hind-part is furnimed with a 

 flender fharp tail. In the middle are orbicular Interlines of dif- 

 ferent fizes ; the larger of them are bright. It's motion is 

 vacillatory ; in fwimming, one edge of the lateral membrane is 

 upwards; the other, folded down. Found in water that has been 

 kept feveral months, 



140. Ccr- 



