EADIOLARIA 847 



and since that time much has been added by various observers to 

 our knowledge of this group, which still remains, however, very 

 imperfect. 



Each individual radiolarian consists of two portions of coloured 

 or colourless sarcode one portion nucleated and central, the other 

 portion peripheral, and almost always containing certain yellow 

 corpuscles. These two portions are separated by a membrane called 

 the capsule ; but this is so porous as to allow of their free communi- 

 cation with each other. The infrier central capsule is also the special 



\ 



FIG. 644. Fossil Eadiolaria from Barbadoes : a, Podocyrtis mitra ; b, 

 Rhabdolithus sceptrum\ c, Lychnocaniu m falciferum ; d, Eucyrtidium 

 tiibulus ; e, Flustrella concentrica ; /, Lychnocanium lucerna ; g, Eucyr- 

 tidium elegans ; h, Dictyospyris clatlirus ; i, Eucyrtidium Mongolfieri ; 

 &, Stephanolithis spinescens ; I, S. nodosa ; ?n, Lithocyclia ocellus ; n, 

 Cephalolithis sylvina ; o, Podocyrtis cothurnata] p, 



organ of reproduction, for it is the intracapsular protoplasm, with 

 the nuclei imbedded in it, which serves for the formation of flagellate 

 spores; the outer capsule has the special office of protecting and 

 providing nourishment for the cell. 1 The pseudopoclia radiate in all 

 directions (fig. 645) from the deeper portion of the extracapsular 

 sarcode ; they have generally much persistency of direction and very 



which extends over 1,800 pages, and is illustrated by 140 plates. In it are described 

 4,318 species, of which 3,508 are new to science. 



1 The structure of the central capsule of Aulacantha has been carefully worked 

 out by W. Karawaiew, in Zool. Anzeig. xviii. (1895), p. 286 and p. 293. 



