Chap, ix.] SKELETOA T S OF RHIZOPODA. 



275 



various Rhizopods, and may take on the most different 

 forms, and even become pigmented. In marine 

 Rhizopods the test becomes much firmer, owing to the 

 deposition in its substance of calcareous salts ; and as 



\ 



Fig. 111. Gromia terricola, showing the Protoplasm extending round 

 the chitinous test. (After Leidy.) 



the test becomes traversed by pore canals, through 

 which there pass processes of the protoplasmic body 

 that has formed it, we get a structure which more 

 easily falls in with our idea of a skeleton. This 

 skeleton may be rounded and simple, or else it may 

 give off fine projecting processes, or it may, as in 

 Orbitolites and other Foraminifera, become 



