GREGARINA—MONOC YSTIS. 



89 



Description. — Two species (M. agilis and M. magna) in- 

 fest the male reproductive organs of the earthworm so con- 

 stantly that we are almost always sure of finding them. 

 The full grown adults are visible to the naked eye. They 

 are usually cylindrical, and frequently much elongated, cells, 

 but the shape alters considerably during the sluggish 

 movements. There is a definite contractile rind, which 

 is sometimes fibrillated, and a central more fluid 



d/g 



Fig. 18.— Life history of Gregarina. (After Butschlt.) 



a.yg. Young forms emerging from intestinal cells. 



ad. Adult with deciduous head cap and a cuticular partition divid- 

 ing cell into two. 



con. Two forms conjugating (G. blattancm). 



sp.f. Spore formation. 



sp-i. Ripe spore of G. bla.tta.rnin. 



sp2. Spore of G. gigantea^ with long vibratile part which breaks off 

 and develops into an adult. 



substance, in which the large nucleus floats. In one 

 species there is an anterior projection which resembles the 

 cap of Gregarina, otherwise unrepresented in Monocystis. 

 As in Gregarina, and many parasitic forms, a contractile 



