448 



Mi croscopical 



Essays. 



of this minute creature is contained within the fhell, fee Fig. 35. 

 The fhell is fo tranfparent that the terminations cannot be eafily 

 diftinguifhed when the animal is extended; but whatever is 

 tranfacled within the fhell, is as plain as if there was no fubftance 

 between the eye and the interior parts. 



Fig. 36, 37, 38, exhibit the appearance of another fpecies of 

 thefe animals, which differs from the foregoing kind. This has 

 alfo a head, a thorax and abdomen, but then they are not fepa- 

 rated by a gut or intermediate veffel, as in the former, but are 

 joined immediately together, and at the place where in the firfi; 

 kind a moveable interline was feen; in this a mufcle, moft 

 probably the heart, may be difcovered 5 it has a regular fyftole 

 and diaftole : this part is intended to be fhewn at a, Fig. 36, 37, 

 38. Like the other it draws the head and tail within the fhell, 

 which then appears to have fix teeth or fpikes on one fide, and 

 two on the other : it very feldom protrudes it's head fo far out 

 as the other ; fometimes the fibrillar may be feen within the mar- 

 gin of the fhell. 



Both fpecies carry their young in an oval integument or bag, 

 fattened externally to the lower part of the fhell, fomewhere 

 about the tail; thefe bags are fometimes opake at one end, and 

 feemingly empty at the other, fee Fig. 34 : r metimes the middle 

 is opake, with a tranfparent margin, fee Fig. 36. 



It is highly entertaining to fee a young one burft it's integu- 

 ment, and gradually force it's way out ; in performing this opera- 

 tion, it is much alfified by the motion of the tail of the parent. 

 The head pari comes out firfl, it then fets it's rotatory organ in 



motion, 



