28 



PROTOZOA. FORAM1NIFERA 



in the Miocene. A large number of forms occur in the 

 Pliocene deposits of East Anglia and of St Erth in 

 Cornwall. 



The genera and species of the Foraminifera have 

 generally, as might be expected from their low organisa- 

 tion, a long range in time ; some of the species which occur 

 in the Palaeozoic are still living. 



ORDER II. RADIOLARIA 



In the Radiolaria the body consists of a central mass of 

 protoplasm, enclosed in a membrane known as the central 



3 



Fig. 5. Heliosphara inermis. x 350. Recent. (After Biitschli.) 1, 

 skeleton ; 2, central capsule ; 3, nucleus. Pseudopodia project from 

 the surface. 



capsule (fig. 5, 2). The intracapsular protoplasm contains 

 one or more nuclei, and is continuous, through pores in 

 the capsule, with a layer of protoplasm outside the cap- 

 sule ; this layer gives off thread-like pseudopodia, which 

 occasionally unite. A skeleton (fig. 5, 1) is generally 

 present, composed either of silica, or a peculiar horny 



