188 



PROTOZOA. 



differentiations of the sarcode, particularly of the central 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 





FIG. 129. Thalassicolla pelagica, with central capsule and single large nude us, also numerous 

 alveoli in the protoplasm (after E. Haeckel). 



after previous conjugation of one or more individuals, also during 

 encystmeiit. Multiplication by spores has also been observed 

 (Clathrulina). 



In the ActinojjJiryidce there is no skeleton secreted : Actinnsphcerium 

 Eichhornii Ehrbg. The central matter contains numerous nuclei. Actinoplirys 

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



In the Acantliocystidts slender silicious spikes, are found: Acanthocysti* 

 spinifera Greeff. with silicious spikes and needles. 



In Clathrulina there is a latticed silicious shell, and ihe body has a stalk 

 Clathrulina elegans Cienk. 



