SEX IN PROTOZOA 181 



tinophrys sol.) Each "primary cyst" divided into two "secondary 

 cysts" ^^•ithin Mhich each nucleus gave off two "polar bodies," one 

 after the other. The pairs of secondary cysts tlien fused inside the 

 primary cyst membrane, thus producing a "conjugation cyst" which 

 included the zygote. The zygote eventually emerged as an active 

 individual. 



In addition to asexual fission and budding, Zuelzer (1909) in- 

 cluded "gamogonie" in the life history of the marine heliozoon, Wag- 

 nereUa borealis. "Gamogonie" was of rare occurrence and involved 

 the formation of "flagellispores" which were presumed to be gametes. 

 There has apparently been no confirmation of this account, so that 

 it remains questionable. Sexuality has thus been fully demonstrated 

 only for Actinopbrys sol and Actinosphaerhnii eichhoriii among the 

 Heliozoa. 



Order Radiohrria 



This group consists of marine members of the Sarcodina, which 

 have radiating pseudopodia like those of the Heliozoa but differ from 

 the latter group by the possession of a membrane, the central cap- 

 sule, between the inner medullary region (endoplasm) and the outer 

 cortical region (ectoplasm). 



Most of the Radiolaria have rigid siliceous skeletons, but one 

 group has skeletons of strontium sulfate. Some kinds have no skele- 

 tons, and others have loose spicules or crystals. Some are colonial in 

 organization. Kudo recognizes four suborders: Actipylea, Peripylea, 

 Monopylea, and Tripylea. 



Some Radiolaria reproduce by binary fission or by budding or 

 even by multiple fission. These processes occur among skeletonless 

 and colonial forms. Some of the Actipylea and Tripylea also repro- 

 duce by binary fission. However, the most characteristic method of 

 reproduction is supposed to be the formation of large numbers of 

 flagellated swarmspores. These are of two types: isospores, usually 

 round, oval, pear- or spindle-shaped, each with a "crystal," which 

 Hertwig stated was organic rather than inorganic, and with one, two, 

 or three flagella (Fig. Q, 2, 3); and anisospores, usually without crys- 

 tals, often bean- or kidney-shaped, with two flagella and appearing 

 in two different sizes in the same species, or even in the same indi- 

 vidual (4, 5). The isospores are believed to represent asexual off- 



