GENERAL ORGANIZATION OF F R AM IN IF ER A. 437 



FIG. 204. 



several such apertures, though it is now more commonly under- 



stood as applying to the sieve-like structure often presented by 



the external shell. It was by M. Dujardin, in 1835, that the 



structure of these animals was first shown to be conformable to 



the Ilhizopod type ; and notwithstanding the opposition to his 



views which has been set up by Prof. Ehrenberg (who, with in- 



explicable pertinacity, has con- 



tinued to rank them among his 



Bryozoa, Chap. XIII), they have 



been confirmed by all subse- 



quent observers, and more espe- 



cially by the recent researches 



of Prof. Schulze, 1 who has given 



admirable descriptions of the 



animals of several different 



kinds of Foraminifera, derived 



from observation of them during 



their living state. The confor- 



mity of the Foraminifera to the 



ordinary Rhizopod type, is best 



seen in those forms, such as 



Grromia (Fig. 204), in which 



there is no multiplication of 



chambers; and it is made ob- 



vious by an examination of the 



accompanying figure, that there 



is no other essential difference 



between Grromia and Arcella or 



Diffugia (Fig. 193), than that 



which lies in the greater length 



and slenderness of the pseudo- 



podial prolongations of the sar- 



code body in the former, as com- 



pared with those of the latter. 



The food is obtained by the ex- 



tension of these pseudopodia in 



Various directions from the 



mouth of the shell ; and the ab- 

 sence of any membrane investing them is clearly indicated by 

 their fusion or coalescence when two or more happen to come 

 into contact, as well as by the vagueness of the expansions into 

 which they are occasionally seen to spread out. These instru- 

 ments entangle and lay hold of the minute bodies which serve as 

 food to the animals, consisting of Diatomacese, Desmidiese, the 

 smaller forms of Confervse, &c. ; and they draw these, by their 

 contraction, into the substance of the body, within which they 

 may be seen through the transparent shell. It is not by any 

 means constantly, that their indigestible residua are cast forth 



1 "tiber den Organismus der Polythalamien (Foraminiferen).'' Leipzig, 1854. 



o^/ormi*, with its pseudopodia extended. 



