SI X IN PROTOZOA 1H7 



Schewiakoff (1926), in liis monographic study of "Acanrharia" 

 collected in the (ailt of Naples, described the development and emis- 

 sion of large numbers of flagellispores from various species. In one 

 case he estimated the number produced at one swarming to be 17,000. 

 These "swarmers" resembled in most respects the isospores described 

 for other groups by previous authors (Fig. Q, 24, 25). They ranged 

 in size from 2 [j. to 10 [j.. Certain species produced swarmers with only 

 one flagellum, others with two unequal flagella, and still others with 

 two equal flagella. Schewiakoff believed these to be gametes but did 

 not actually observe fusion. He did, however, find among ordinary 

 biflagellated swarmers some of double size with four flagella and two 

 nuclei and others with four flagella and only one large nucleus. This 

 series (Fig, Q, 26 to 28) was thought to show gamete fusion to form 

 zygotes. He \vas unable to observe any development of these "zy- 

 gotes." 



x\lthough I have not examined all the papers dealing with the 

 life history of the Radiolaria, of those reviewed Schew^akoff's ob- 

 servation of "double" flagellispores appears to be our only direct 

 evidence for sexuality in the Radiolaria. However, if this interpre- 

 tation is correct, it may be that the isospores of other Radiolaria may 

 be gametes and that fusion fails to take place between gametes pro- 

 duced bv the same parent, as seems to be true in the dinoflagellates. 

 Surely this whole subject of sexuality in the Radiolaria is in need of 

 extensive reinvestigation. 



CLASS SPOROZOA 



The literature on reproduction in this parasitic and spore-bearing 

 group of Protozoa up to about 1930 has been monographically 

 treated by Naville (1931), who provides a much more complete re- 

 view than can be attempted here. Older reviews are those of Biitschli 

 (1882-89), of Balbiani (1884), and of Labbe (1899). 



Kudo segregates the Sporozoa into the subclasses Telosporidia, 

 Cnidosporidia, and Acnidosporidia. In the Telosporidia and Cnido- 

 sporidia sexual reproduction is well-known; it usually alternates with 

 various forms of asexual reproduction. The Subclass Telosporidia 

 consists of three orders, Gregarinida, Coccidia, and Haemosporidia, 

 with intermediate groups linking them together. 



In the Schizogregarinaria, Coccidia, and Haemosporidia, asexual 



