372 



THE MICROSCOPE. 



history of these minute parasites, are well worthy of 

 investigation. 



The Rhizopoda appear as creatures of a low type of 

 organization, and are considered, with the former, to hold 

 a medium state between animals and vegetables. Almost 

 all of them live in water ; it would be a fruitless search 

 to look for distinct internal organs, as the small bladder- 

 looking spaces enclosed within their substance, believeo 

 by Ehrenberg to be stomachs, present only the appear- 

 ance of transparent gelatinous cells, or rather moving 

 spaces, within the sarcode envelope, and may be regarded 

 as the earliest dawn of a circulatory system. 



The term Rhizopoda is derived from the Greek, and 



Fig. 205. Simple Rhizopods. 



A, Difflugia proteiformis. B, Difflugia oUonga. c, D, Arcella acuminata and 

 dentata. 



means "root-footed," the body is composed entirely of 

 gelatinous matter, sarcode, motion being effected by the 

 extension of portions of the substance into processes, 

 which, as in fig. 205, is seen to partake of various forms. 



Lobosa. In the deposit formed at the bottom of fresh- 

 water ponds, we may often meet with a singular minute 

 gelatinous body, which constantly changes its form even 

 under our eyes ; and moves about by means of finger-liko 

 processes, called pseudopodia, which it appears to have tho 

 power of shooting out from any part of its substance. 



