PROTOZOA. 



265 



The Rhizopoda appear as creatures of a low type of 

 organisation, 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-look- 

 ing spaces enclosed within their substance, believed by 

 Ehrenberg to be stomachs, and which have been termed by 

 Dujardin sarcode, present only the appearance of a trans- 

 parent gelatinous cell, with or without moving spaces in 

 their interior, which may be regarded as the earliest dawn 

 of a circulatory system. 



The term Ehizopoda is derived from the Greek, and 



Fig. 162. Simple Rhizopods. 



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

 dentata. 



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

 gelatinous matter, sarcode, motion being effected by the 

 extension of portions of their substance into processes, 

 which partake of various forms. 



Amoeba. 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-like 

 processes, called pseudopodia, which it appears to have the 

 power of shooting out from any part of its substance. 

 This shapeless mass is well known to microscopic observers 



