630 Microscopical Essays. 



horn proceeds, which cannot be feen unlefs the infect turns on it's 

 back or fide. 



Below the thorax there is an annular circle that joins the tho- 

 rax to the abdomen. The abdomen is much the largeft part of 

 this animal, it contains the flomach and vifcera. When this 

 creature is full of food, the bowels are opake, and of a crimfon 

 colour, extending from the thorax quite through the belly and a 

 great part of the tail, and exhibits a fine view of the periftaltic 

 motion, or thofe gradual contractions and dilatations of the intef- 

 tines, which propel their contents downwards. There are many 

 ramifications of vefiels, both longitudinal and tranfverfe, round 

 the bowels. It can extend the abdomen in length very much, or 

 contract and widen it confiderably, fo as to become a cafe for all 

 the reft of the body. The tail goes from a joint at the lower part 

 of the belly to the pofterior extremity ; it is of a tapering form, 

 and confifts generally of three joints ; when it is inclined to fix 

 itfelf to any thing by the tail, it thrufts out four, fometimes fix, 

 little hooks from the end thereof ; tlrefe are placed in pairs, one 

 pair at the very extremity itfelf, the other two a little way up the 

 fides ; the three are feldom feen at the fame time. The wheels 

 feem to be the organ that the animal ufes to allift it in fwim- 

 ming. 



All the actions of this creature feem to imply fagacity and 

 quicknefs of fenfation ; at the leaft touch or motion in the water 

 they inftantly draw in their wheels. Mr. Baker conjectures that 

 they have eyes lodged near the wheels, becaufe while they are in 

 the globular or maggot ftate, their motions are flow and blunder- 

 ing; 



