ORDER II 



RADIOLARIA 



37 



Order 2. RADIOLARIA. Miiller. 1 

 (Polycystina, Ehrenberg.) 



Uhr.opoda emitting fine, filiform, radially directed pseudopodia, with 

 capsule and extra-capsulum, and usually with delicate silicious skeleton. 



The sarcode body of the Radiolarians is differentiated into (1) an inner 

 -.Mitral sphere or capsule of tough slimy protoplasm containing one or more 

 nuclei, vacuoles, alveoles, granules, oil-globules, and sometimes crystals, and 

 surrounded by a capsule-membrane perforated by pores or pylae ; and (2) an 

 outer jelly-like extra-capsulum. the sarcode of which emits pseudopodia. The 

 individuals lead usually an isolated existence, and are only rarely united in 

 colonies. 



Must Radiolarians secrete skeletons composed either of bars or spicules of 

 (an organic substance allied to horn or chitin) or silica, or they build 

 an exceedingly delicate lattice-work composed of transparent amorphous silica. 

 Only the latter forms are known in a fossil state, and owing to their minute 

 size, are commonly indiscernible except with the aid of the microscope. 



1 Khrenberg, C. G., Mikrogeologie, 1854, and Abhandlg. Berliner Akad. 1875 (Radiolaria from 

 Karliados). Haeckel, E., Die Kadiolarien. Monograph 1862, and Report on the Radiolaria col- 

 lected l.y II. .M.S. Challenger, ISSl.Hertwig, Ji., Der Organismus der Radiolarien, 1879. 

 >'/;///, E., Palaeontographica, XXVI. 1878 (Radiolaria from Sicily). 7? list, D., Palaeontographica, 

 XXXI. 1885, XXXIV. 1888, and XXXVIII. 1892. Drei/er, /'., Die Tripoli von Csiltanisetta. 

 Jsnaische Zeitsclirift f. Xaturw. XXIV. ISQQ.Cayeux, L., Bull. Geol. Soc. France, 1894, p. li7. 



