SPOROZOA, TELOSPORIDIA, COCCIDIA 267 



encyst together and the nucleus in each divides repeatedly to 

 form numerous gametes. The gametes fuse in pairs with those 

 produced in the other gametocyte within the common envelope. 

 The zygotes develop into spores, each containing sporozoites 

 of variable number. When these spores enter a new host, the 

 changes outlined above are repeated. The Telosporidia are 

 parasitic in vertebrates and higher invertebrates. 



The subclass is divided into three orders, as follows: 



Mature trophozoite intracellular and small 



Zygote non-motile; sporozoites within spore Order 1 Coccidia 



Zygote motile; sporozoites without envelope Order 2 Haemosporidia 



Mature trophozoite extracellular, large; zygote non-motile; sporozoites 



in spore Order 3 Gregarinida 



ORDER 1 COCCIDIA LEUCKART 



The Coccidia show a wide zoological distribution, attacking 

 the vertebrates and higher invertebrates alike. The majority 

 are parasites of the epithelium of the digestive tract and its 

 associated glands. Asexual reproduction is by schizogony and 

 sexual reproduction by anisogamy in the majority of species. 

 Both kinds of reproduction take place in one and the same host 

 body, with the exception of such forms as Aggregata. 



The Coccidia are ordinarily divided into two suborders: 



Gametocytes similar in size; independent; each microgametocyte de- 

 veloping into numerous microgametes Suborder 1 Eimeridea 



Gametocytes dissimilar; associated with each other during the latter 



part of trophic life; a few microgametes Suborder 2 Adeleidea 



Suborder 1 Eimeridea Leger 



These Coccidia are, as a rule, intracellular parasites of the 

 epithelium of the digestive tract of the hosts. In many of 

 them, there occurs an alternation of asexual (schizogonic) and 

 sexual (sporogonic) generations. In some there is also alterna- 

 tion of hosts. 



As an example of the life-cycle of a typical coccidian, that of 

 Eimeria schubergi, a parasite of the intestine of the centipede, 

 Lithohitis forficatus, as worked out by Schaudinn, may be stated 

 here briefly (Fig. 109). The infection begins when the oocysts 

 of the coccidian gain entrance into the host through the mouth. 



