KADIOLARIA. 



189 



Order 3. RADIOLARIA.* 



Marine Rhizopoda with complicated differentiation of the sarcode 

 body, with central capsule and radial silicious skeleton. 



The sarcode body contains a membranous porous capsule (the 

 central capsule), in which is contained a tough slimy protoplasm 

 with vacuoles and granules (intracapsular sarcode), fat and oil 

 globules, and albuminous bodies, and more rarely crystals and con- 

 cretions. The intracapsular mass contains also a single large nucleus 

 or several small nuclei. The sarcode which surrounds the capsule 

 and which emits on all sides simple or anastomosing pseudopodia, 

 contains numerous yellow cells, sometimes pigment masses ; and in 

 some cases delicate trans- 

 parent vesicles, or alveoli, 

 are found in the peripheral 

 layer between the radia- 

 ting pseudopodia (Thalas- 

 sicolla pelayica, fig. 129). 



Many Radiolaria form 

 colonies, and are composed 

 of numerous individuals. 

 In such colonies the al- 

 veoli are placed in the 

 common protoplasm, 

 which contains in itself, 

 not as in the monozoic -; ; i ; . 



Radiolaria a single cen- ( 



tral capsule, but a number FlR iso.Acanthometra mileri (after E. Haeckel). 



of capsules. Only a few 



species remain naked and without firm deposits ; as a rule, the soft 

 body possesses a silicious skeleton, which either lies entirely outside 

 the central capsule (Ectolithia) or is partially within it (Entolithia}. 

 In the most simple cases the skeleton consists of small, simple, or 

 toothed silicious needles (spicula) united together, which sometimes 

 give rise to a fine sponge work round the periphery of the proto- 

 plasm, e.g., Physematium. In a higher grade we find stronger hollow 

 silicious spicules, which radiate from the middle point of the body 

 to the periphery in regular number and order, e.g., Acanthometra 



* Joh. Miiller, " Ueber die Thalassicoilen, Polycystinen und Acanthometren," 

 Abh. dcr Bcrl. Akad. 1858. E. Haeckel, " Die Kadiolarien," Eine Monographic 

 Berlin, 1862. 



