EHIZOPODA. 



29 



the possession of an outer case or shell, and for a long time Ihoy wei'e 

 known to naturalists by their shells alone. As the shell or test is 

 xisnally very beautiful and often very complex, the Foraminifera were 

 consequently placed at first amongst the true shell-fish (Mollusca), 

 very much in advance of their true position. When, however, the 

 anatomical structure of the group came to be investigated, it was 

 soon found that they were really referable to the Protozoa, and that 



Fig. 8.— Foraminifera. a The animal of Nonionina, after the shell has bean removed 

 by a weak acid ; b Grotnia (after Scliultze), showing the shell surrounded l>y a net- 

 work of filaments derived from the body-substance. 



in point of fact they even occupy a low position in this sub-kingdom. 

 However elaborate and complicated the shell may be, the body of 

 the contained animal is composed simply of granular gelatinous sar- 

 code, highly elastic and contractile, and usually reddish or yellowish 

 in colour (fig. 8, a). This sarcode not only fills the shell, but also 

 in many cases gains the exterior by means of little perforations in 

 its walls, and forms a thin film over its outer surface. Wherever 



