SEX IN PROTOZOA 197 



gamonts (17). Both increase in size (18) until rhcy arc mature; then 

 four microganictes are produced by the microgamont (19). One of 

 these fertihzcs the niacroganiete (20) to produce the zygote (1). In 

 the Kinieridca, ganionts develop independently, as in Air^regata 

 chert hi (Fig. \'/l2 to 18). 



Order Haemosporidia 



Typical members of this group, as found in the Plasmodiidae and 

 Haemoproteidae, have life cycles similar to those of the Eimeridea 

 among the Coccidia, except that two hosts are involved and sporocysts 

 are not formed. In vertebrate hosts asexual reproduction by schi- 

 zogony takes place, and gametocytes (gamonts) are formed which do 

 not proceed further in their development until taken into the digestive 

 tract of the proper blood-sucking invertebrate host, in which sexual 

 reproduction and sporozoite formation take place. In the Babesiidae, 

 or at least in the genus Babesia, asexual reproduction may be by bin- 

 ary fission instead of multiple fission, and the sexual stages occur in 

 ticks. There does not seem to be any satisfactory account of meiosis 

 or chromosome cycles in the Haemosporidia. 



Subclass Cnidosporidia 



In this subclass the sporozoites (sporoplasms) are amoeboid, as 

 are often the trophic stages; thus the group shows affinities with the 

 Sarcodina. The spores contain polar capsules in each of which there 

 is a coiled filament which is discharged upon appropriate stimulation. 

 In some of the Adicrosporidia and in the Helicosporidia the coiled 

 filament is not enclosed in a capsule. Kudo divides the Cnidosporidia 

 into the orders iMyxosporidia, Actinomyxidia, Microsporidia, and 

 Helicosporidia. 



Order Myxosporidia 



Figure W provides a diagrammatic representation of the life 

 cycle of Ceratoviyxa blemmis (Noble, 1941). A binucleate sporo- 

 plasm (1) emerges from the spore which has entered the digestive 

 tract of a new individual host {Hypsoblennius gilberti). Its haploid 

 nuclei fuse and the zygote (2) migrates to the gall bladder of the 



