MONOGYSTIS 



Monocystis, one of the Sporozoa, is a common internal parasite in the 

 reproductive organs of the earthworm (Lumbricus). 



Cut open an earthworm (dorsal side) under salt solution. Open into the 

 median seminal vesicles so as to expose the internal funnel openings of the vasa 

 deferentia. Frequently Monocystis magna (one or several) is seen attached to 

 the funnel by one end ; it looks like a tiny whitish thread. 



Form and Structure of Monocystis magna. 



Carefully remove a specimen, along with the portion of funnel to which it is 

 attached, and place it in a drop of salt solution on a slide. Put on a cover-slip, 

 and examine under low power. 



It is worm-like, and about a quarter of an inch long. Notice the clear thin 



A 



Fig. 3. —Life-history Stages of Monocystis agilis (highly magnified). With permission from 

 Parker and Haswell's Text-hook of Zoology. 



A. Three trophozoites ; B. Cyst containing two gametooytes ; C. Stage prior to formation of gametes. Note the numerous 

 small nuclei. D. Gametocytes broken up and gametes formed. Some of the gametes are conjiigating in pairs, some 

 pairs have fused to form zygotes ; E. Cyst containing ripe spores or pseudonavlcella; ; P. A single spore or pseudo. 

 navicella containing falciform sporozoites ; G. A sporozoilie inside a sperm-morula ; H. A young trophozoite coated 

 with tails of destroyed sperms. 



outer cortex of contractile ectoplasm, the outermost layer of which forms a 

 stiff pellicle. The inner mass of endoplasm, the medulla, is finely granular and 



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