128 MOUTHS OF ANIMALCULES. 



swallowed. In .these species, the mouth does not 

 appear to be surrounded with cilia, which would be 

 unnecessary, but which, when the mouth is a 

 simple orifice, are required for the direction of the 

 food to it. The proboscis of some animalcules is 

 situated, as we have seen, at the anterior extremity 

 of these microscopic beings : this portion, Ehren- 

 berg says, is cleft so as to represent a two-lipped 

 mouth ; the upper lip, bearing the proboscis, being 

 very readily distinguished. 



The term polygastrica, by which the present group 

 is distinguished, refers to the supposed complexity of 

 the digestive apparatus, which is stated to consist of 

 a number of internal sacs, or stomachs ; in some, 

 arising from the mouth itself by separate tubes, in 

 others, appended to a kind of intestinal canal, which 

 traverses the body, and terminates either at the 

 extremity of the body opposite to the mouth, as in 

 Paramecium aurelia, or which, winding up, 

 terminates in a depression near the mouth, as in 

 vorticella. 



The sacs, though distinguishable in the animals 

 under ordinary circumstances, are rendered more 

 conspicuous when the animals have swallowed 

 water in which colouring matter is suspended, in a 

 state of very minute division, but not chemically 

 dissolved. Trembley, in his investigation of the 

 structure of the hydra, adopted this method, and 

 Gleicher attempted it, though unsuccessfully, in his 

 investigations as to these animalcules. The fact is, 



