Microscopical Essays. 



5*3 



degree. At the upper part there are two little moveable pieces, 

 or nipples, a a, between which an empty fpace b is formed, that 

 terminates in the mouth ; the hinder-part is round, but ther.e 

 projects from it a fhort fetaceous tail w ; in the young eels the 

 termination of the tail is not fo abrupt as in the prefent fpecimen, 

 but it finifhes by a gradual diminution. There is probably a vent 

 near z, for the palfage of the excrements ; becaufe when that 

 part has been gently preffed, two or three jets, of a very fubtle 

 fub (lance, have been obferved to iffue from it. If the preffure is 

 increafed, a fmall bladder will be forced out, a further compreffion 

 burfts the bladder, and the bowels are forced through the 

 opening. 



A greater degree of magnifying power is neceffary to obtain an 

 exacl idea of the vifcera of thefe eels. Fig. 10 reprefents the 

 alimentary duel (further magnified) from it's origin to the belly. 

 It is {hewn here as feparated from the animal, which is eafily 

 effeaed; for nature, affifted by very little art, performs the 

 operation. The oefophagus, b c, Fig. 6 and 10, at it's origin 

 a a, is very fmall, but foon grows larger, as at c, and forms a 

 kind of oblong bag, cd; the diameter of this increafes till it 

 comes to d, where it fwells out as at de f ; it then grows fmdler 

 till it comes to g, when it again fwells out as g k 1. There is a 

 narrow neck at i, which in it's natural ftate is feen in the bag k 1. 

 The part k 1 is the ftomach. M. Becli has fhewn, that the ali- 

 mentary duel of many fpecies of worms is formed of two bags 

 one of which is inclofed within the other. It is the fame with 

 this animalculum ; the little veflel be, that we have called the 

 oefophagus, which is the origin of the bag c d, enters into the 

 lame bag, and preferves it's form within it, till it comes to in, 



3 R • from 



