OF ANIMALCULES. 193 



a recent paper of his*, that he had now filled up this^ va- 

 cancy. I would remark also, that in his original table, 

 the Monads are the only genus admitted by him into the 

 first family : the others which I have inserted are from 

 Dr. Ehrenberg's notes. 



(t) POLYGASTRICA.— The animalcules included in 

 this class are the most numerous. They are separated 

 into two grand divisions : the Anentreta, in which the 

 digestive sacs are not attached to an alimentary canal, 

 but are connected all of them with the oral cavity, their 

 only channel of communication^ the Enterodelay in 

 which the sacs are connected to a tubular membrane, or 

 alimentary canal, which latter assumes three forms : the 

 first, and simplest, is that shewn at fig. 41, called Ortho- 

 coela, and is nearly straight. The second, the Campy- 

 locoela, in which it takes a serpentine course, as shewn 

 in figure 159. The third, the Cyclocoela, in which the 

 form is nearly circular, returning into itself, as in the 

 Convallaria citrina ; (see figure 202.) 



In several of the Polygastrica, eye-like spots have 

 been discerned, as in the genera Euglena, Ambl^ophis, 

 and Distigma, which would induce the belief of the ex- 

 istence of a nervous system. These eyes clearly shew 

 that the Microscope is really improved of late, as they 

 were not seen in any of the old construction : this is 

 borne out by that excellent paper of Dr. Grant's, in 

 Vol. X. of Brewster's Edinburgh Journal, where he has 

 given a very correct description of the Cercaria (see 183), 

 but has not observed its bright orange brown eye, so dis- 

 tinctly seen in an Aplanatic Engiscope. 



(t) ROTATORIA.— The alimentary structure of this 

 highly- organized class is separated into four kinds. The 



* Berlin Trans. 1832, abstracted iu the Edin. Phil. Journ. Vol. XV. 



