6G GENERAL HISTORY OF 



Section XXVI. — Digestive System of Polygastrica. 



The most remarkable feature in this class of beings is 

 the reception of food. In most creatures it enters one 

 common cavity, and therefore forms one mass. In the 

 Nais (see Notes on Natural History, plate 7), and some 

 other animals, the alimentary canal is enlarged at intervals, 

 so that it may be termed a percurrent digestive organ ; 

 but in the Polygastrica, it appears to be a very compound 

 organ, sometimes consisting of upwards of two hundred 

 cavities or sacs, as in the Paramecium, while the smallest 

 number is four, and this occurs in the genus Monas. 



The manner in which these sacs are arranged is various, 

 though all may be disposed under two grand divisions, 

 namely : — 



Anentera, or those without a true alimentary canal, in 

 which the refuse of the food is regurgitated, as in the 

 Zoophites, of which the fresh water Polypi {Notes on 

 Nat. Hist. pi. 6) may be taken as an example. It will 

 appear, that the Infusoria belonging to the first twelve 

 families include the Anentera ; these possess but one 

 orifice for the reception and expulsion of food ; and 

 although the mode in which the stomach cells are attached 

 together is not satisfactorily determined (and this I infer 

 from the omission of illustrative figures of structure in 

 Die Infusionsthierchen), yet observation leaves little doubt 

 that no true alimentary canal exists. 



Enterodela, or those Polygastrica possessing a true 

 alimentary canal, constitute the ten remaining families. In 

 this division, the alimentary canal, during its course, sends 

 forth, at intervals, short branches, each of which is termi- 



