SPOROZOA, GREGARINIDA 



379 



ment from the host organ-cavity through osmosis. The vast 

 majority of gregarines do not undergo schizogony and increase 

 in number is carried on solely by sporogony. In a small group, 

 however, schizogony takes place as well as sexual reproduction 

 and this is used as the basis for grouping these protozoans into 

 two suborders as follows: 



No schizogony Suborder 1 Eugregarinina 



Schizogony occurs Suborder 2 Schizogregarinaria (p. 409) 



Suborder 1 Eugregarinina Doflein 



This suborder includes the majority of the so-called gregarines 

 which are common parasites of arthropods. When the spore 

 gains entrance to a suitable host, it germinates and the sporozoites 

 emerge and enter the epithelial cells of the digestive tract. There 

 they grow at the expense of the host cells which they leave soon 

 and to which they become attached by various organellae of 

 attachment (Fig. 174). These trophozoites become detached from 



Fig. 174. The life-cycle of Lankesteria culicis, X about 500 (Wen- 

 yon), a, entrance of sporozoites into the epithelial cell and growth 

 stages of trophozoites; b, mature trophozoite; c, association of two 

 trophozoites; d-f, gamete-formation; g, gametogony; h, development 

 of spores from zygotes; i, a spore; j, germination of spore in host gut. 



the host cells and move about in the lumen of the gut. This stage, 

 sporadin, is ordinarily most frequently recognized. It is usually 

 large and vermiform. The body is covered by a definite pellicle 



