I'OLYGASTHICA. 



57 



Fig. 18. 



n 



are appended : sometimes the 



mouth and anus are lodged in 



the same fossa, and the intes- 

 tinal canal forms a circle in the 



body (ANOPISTHIA, Ehren.), as 



in the Vorticella (Jig. 18, 2) : or 



else the mouth and anus are placed 



at opposite extremities of the body, 



through which the intestinal tube 



passes either in a straight course, * 



or exhibiting several flexuous curves 



in its passage. (ENANTIOTRETA 



and ALLOTRETA, Ehren.) (fig- 



18, 3 and 4.) When neither the 



mouth nor anus are terminal, as 



in Kolpoda, (Jig. 19 ; 7, a, ,) 



such animals belong to the group 

 denominated KATOTEETA by the 

 same author. 



(81.) However imposing, from their completeness, the views of 

 Ehrenberg concerning the digestive system of the polygastrica may 

 be, and sanctioned as they are by almost general consent, we can- 

 not pass over a subject of so much importance without expressing 

 ourselves as being far from admitting their accuracy in all respects, 

 and we must say that our own observations upon the structure of 

 the polygastrica have led us to very different conclusions.* 



The positions of the mouth and anal aperture we are well 

 assured, by frequent examination, to be such as are indicated by 

 the illustrious Professor of Berlin ; but with regard to the tube 

 named by him intestine, and the stomachs appended thereto, our 

 most patient and long-continued efforts have failed to detect the 

 arrangement depicted in his drawings. In the first place, as re- 

 gards the function of the sacculi, which he looks upon as the organs 

 in which digestion is accomplished ; in carnivorous animalcules 

 which devour other species we might expect, were these the 

 stomachs, that the prey would at once be conveyed into one or 

 other of these cavities ; yet, setting aside the difficulty which must 

 manifestly occur in lodging large animalcules in these microscopic 



* It may be proper to state that the microscope used in these and similar re- 

 searches to which allusion will be made, is a compound achromatic, made by Ross 

 of London ; and the powers employed, of -&, , ^, and $ of an inch focus. 



