144 



CHAPTER IX. 



PROTOZOA — Continued. 

 Radiolaria. 



The order of the Radiolarians comprises a vast number of Rhizo- 

 pods, in which the sarcode-body consists of a central protoplasmic mass, 

 enclosed in a porous, membranous, or chitinous capsule, which is in 

 turn surrounded by a thick layer of sarcode. The intra-capsular sar- 

 code contains a central " nucleus," and the pseudopodia (fig. 44) have 

 the form of slender radiating filaments, which rarely anastomose with 



Fig. 44. — Eiicecryphalus Schultzei, with the pseudopodia extended, showing the perforated 

 siliceous test and the lobed protoplasmic body. (After Kolliker.) 



one another. As a rule, the protoplasmic body secretes a radially 

 disposed skeleton composed of silica, of a silicate, or of a horny sub- 

 stance (." acanthin "). 



As regards the skeleton of the Radiolarians, some forms (Thalas- 

 sicolla, Thalassolampe, Collozoum, &c.) are wholly devoid of hard 



