202 SEX IN MICROORGANISMS 



(1943) found a diploid number of about twelve chromosomes with a 

 meiotic division preceding sporogony. Just when fusion of gametes 

 occurred was not determined. Much more study is needed to elucidate 

 the problems of syngamy in the Microsporidia. 



Order Helicosporidia 



This order consists of one species, HeUcosporidiiim parasiticmn, 

 the life cycle of which has not been fully worked out. 



Subclass Acnidosporidia 



In this subclass, as presented by Kudo, there are two orders, the 

 Sarcosporidia and the Haplosporidia. No sexual stages have been 

 determined for the Sarcosporidia. 



Order Haplosporidia 



This group shows some similarities to certain members of the 

 Microsporidia, but the spores are simple, not having any polar cap- 

 sules or polar filaments. Accounts of the life cycles are usually incom- 

 plete. For Ichthyosporidiimj giganteim?, Swarczewsky (1914) de- 

 scribed a life cycle which included meiosis and fertilization within 

 the sporobkist during development of the spores. This would presum- 

 ably involve pregametic meiosis. A similar life cycle is claimed by 

 the same author for Ichthy osporidiinn herfwigi and for Pleistophora 

 periplanetae. Granata (1914) has described gametogenesis in Haplo- 

 sporidiimi Uvmodrili. The gamete fusion stages are shown in Fig. X 

 (10 to 13). Gametes are formed (10) and fuse (11, 12), producing 

 zygotes which become spores (13). Although these life histories are 

 not so complete as desired, at least they show evidence for the forma- 

 tion and fusion of gametes. 



Comments on Sexuality in the Sporozoa 



Certain topics in connection with syngamy in the Sporozoa merit 

 separate discussion. Two of these are (1) sex determination and sex 

 differentiation, and (2) the effect of the host on life cycles. 



