150 FORAMINIFERA, RADIOLARIA, AND DIATOMS 



in order to get some notion of the great amount of dif- 

 ferentiation attained by the shells of these extremely simple 

 organisms. 



The Radiolaria form another group of marine animal- 

 cules, the numerous genera of which are, like the Foram- 

 inifera, amongst the most beautiful of microscopic objects. 

 They also (Fig. 34) consist of a mass of protoplasm giving 



-Int. Caps.pr 

 cent caps 



FIG. 34. Lithocircus anintlaris, one of the Radiolaria, showing 

 central capsule (cent, caps.}, intra- and extra-capsular protoplasm (int. 

 caps, pr, ext.caps.pr}, nucleus (nn], pseudopods ( psd), silicious skeleton, 

 (skel), and symbiotic cells of Zooxanthella (2). (After Biitschli.) 



off numerous delicate pseudopods (psd} which usually have 

 a radial direction and sometimes unite to form networks. 

 In the centre of the protoplasmic cell-body one or more 

 nuclei (mi] of unusual size and complex structure are 

 found. 



In the interior of the protoplasm, surrounding the nucleus, 

 is a sort of -shell, called the central capsule (cent, caps.), 

 formed of a membranous material and perforated by pores 

 which place the inclosed or intra-capsular protoplasm (int. 



