370 PROTOZOOLOGY 



also known to occur in Thalassophysidae in which it is the sole 

 known means of reproduction. The central capsule becomes very 

 irregular in its outline and the nucleus breaks up into numerous 

 chromatin globules. Finally the capsule and the intracapsular 

 cytoplasm become transformed into numerous small bodies, each 

 containing several nuclei. Further changes are unknown. 

 Swarmer-formation is known in some forms. In Thalassicolla, 

 the central capsule becomes separated from the remaining part 

 of the body and the nuclei divide into a number of small nuclei, 

 around each of which condenses a small ovoidal mass of cyto- 

 plasm. They soon develop flagella. In the meantime the capsule 

 descends to a depth of several hundred meters, where its wall 

 bursts and the flagellate swarmers are liberated (g). Both iso- 

 swarmers and anisoswarmers occur. The former often contain 

 a crystal and a few fat globules. Of the latter, the macroswarmers 

 possess a nucleus and refringent spherules in the cytoplasm only. 

 Some forms possess 2 flagella, one of which is coiled around the 

 groove of the body, w^hich makes them resemble certain dino- 

 flagellates. Further development is unknown; it is supposed that 

 the anisoswarmers are sexual and isoswarmers asexual genera- 

 tions. 



Enormous numbers of species of Radiolaria are known. An 

 outline of the classification is given below, together with a few 

 examples of the genera. 



Skeleton composed of strontium sulphate 



Suborder 1 Actipylea 



Skeleton composed of other substances 



Central capsule uniformly perforated; skeleton either tangential to 

 the capsule or radiating without reaching the intracapsular 



region Suborder 2 Peripylea (p. 372) 



Central capsule not uniformly perforated 



Capsule monaxonic, bears at one pole a perforated plate forming 



the base of an inward-directed cone 



Suborder 3 Monopylea (p. 373) 



Capsule with 3 openings: 1 astropyle and 2 parapyles 



Suborder 4 Tripylea (p. 374) 



Suborder 1 Actipylea Hertwig 



Radial spines, 10-200, not arranged according to Mliller's law 



Legion 1 Actinelida 



Spines radiate from a common center; ancestral forms (Haeckel) . . 

 Family 1 Actineliidae 



