188 



I'KOTOZOA. 



differentiations of the sarcode, particularly of tlie centra] capsule. 

 One or more nuclei may be present in the central mass. An im- 

 portant distinguishing mark is afforded by the presence of the 

 pulsating vacuoles, which have not been observed in any marine 

 Radiolarian. 



The reproduction very frequently takes place by fission, occasionally 



FIQ. 129. Thalasslcolla pelagica, with central capsule and single large nucleus, also numerous 

 alveoli in the protoplasm (after E. Haeckel). 



after previous conjugation of one or more individuals, also during 

 encystnient. Multiplication by spores has also been observed 

 (Clathrulina). 



In the Actinojthryidcn there is no skeleton secreted : AetinospTicerivm 

 Eiclihornii Ehrbg. The central matter contains numerous nuclei. Actinoplirys 

 sol Ehrbg. of small size, with a single central nucleus. 



In the AcantUocystidee slender silieious spikes are found : Acantliocysti* 

 aplnife.rn Greeff. with .silicious spikes and needles. 



In CJathrulinaihcTQ is a latticed silicious shell, and the body has a stalk 

 Clathrulina elrgans Cienk. 



