NUTRITION IN THE INFUSORIA. 



73 



among this order of beings. Whole generations of these 

 transparent gelatinous animalcules may remain immersed 

 for weeks in an indigo solution, without presenting any co- 

 loured points in their tissue, except the circumscribed cavi- 

 ties above described. 



Great variety is found to exist in the forms, situations, 

 and arrangement of the organs of digestion in the Infusoria. 

 They differ also in their degree of complication, but with- 

 out any obvious relation to the magnitude of the animalcule. 

 The Monas alomus, the minutest of the whole tribe, exhi- 

 bits a number of sacs, opening by as many separate orifices, 

 from a circumscribed part of the surface. In others, as in 

 the Leucophra patula, of which Fig. 25 represents the ap- ~ 

 pearance under the microscope, there is a long alimentary 



255- 



canal, traversing the greater part of the body, taking several 

 spiral turns, and furnished with a great number of blind 

 pouches, or caeca, as sacs of this description, proceeding la- 

 terally from any internal canal, and having no other outlet, 

 are technically termed. These cavities become filled with 

 coloured particles immediately after their entrance into the 

 alimentary canal; and must, therefore, be considered as so 

 many stomachs provided for the digestion of the food which 

 they receive.* But they are not all filled at the same time, 



* Ehrenberg terms these Polygastric infusoria, from the Greek, signify- 

 ing with many stomachs. 



VOL. II. 10 



