378 PROTOZOOLOGY 



Subclass 1 Telosporidia Schaudinn 



The spore which contains neither a polar capsule nor a polar 

 filament, possesses one to several sporozoites and is formed at the 

 end of the trophic life of the individual. In the forms which invade 

 two host animals to complete their development, there occur 

 naked sporozoites instead of spores. 



The infection of a new host begins with the entrance of mature 

 spores through mouth, or with the introduction of the sporozoites 

 by blood-sucking invertebrates directly into the blood stream. 

 The sporozoites enter specific host cells and there grow at the 

 expense of the latter. In the Coccidia and the Haemosporidia 

 the schizont continues its intracellular existence, but in the 

 Gregarinida it leaves the host cell and grows in an organ cavity. 

 Except Eugregarinina, the vegetative form undergoes schizogony 

 and produces a large number of schizonts which invade new host 

 cells, thus spreading the infection within the host body. The 

 schizonts finally develop into gametocytes. In the Coccidia and 

 the Haemosporidia, anisogametes are, as a rule, produced. Each 

 macrogametocyte develops into a single macrogamete and each 

 microgametocyte, into several microgametes. Fusion of two 

 gametes results in formation of a large number of zygotes, each 

 of which develops either into one to many spores or into a number 

 of naked sporozoites. In the Gregarinida, two fully mature 

 trophozoites (or gametocytes) encyst together and the nucleus 

 in each multiplies repeatedly to form numerous gametes, which 

 fuse in pairs with those produced in the other individual within 

 the common envelope. The zygotes develop into spores, each con- 

 taining 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. 



Three orders are distinguished in this subclass: 



Mature trophozoite extracellular, large; zygote not motile; sporozoites 

 enveloped Order 1 Gregarinida 



Mature trophozoite intracellular, small 



Zygote not motile; sporozoites enveloped . Order 2 Coccidia (p. 415) 

 Zygote motile; sporozoites naked. .Order 3 Haemosporidia (p. 434) 



Order 1 Gregarinida Lankester 



The gregarines are chiefly coelozoic parasites in invertebrates, 

 especially arthropods and annelids. They obtain their nourish- 



