MONOCYSTIS 155 



about for a short time in the worm's sperm-sacs, the free 

 and mature Monocystis conjugates and, encysts. Two 

 individuals come together, and are attached to one another 

 by their broader ends. In this condition each individual 



Fig. 32. 



A , a free specimen of Monocystis agiUs \ nu, nucleus. S, sperm- 

 mother cells adhering to the parasite. i3, a free monocystis 

 covered with ripe spermatozoa, and thus appearing as if covered 

 with a coat of long cilia. C, a ripe cyst of Monocystis agilis 

 containing numerous pseudonavicellae/j. (A and B, original ; 

 C, after Lankester.) 



is termed a zygote (Greek vyr), a yoke, because the two 

 are yoked or joined together). The zygotes contract into 

 spherical form, and each contributes to the formation of a 

 common transparent protective case or cyst-wall, composed 

 of chitin-like substance. At first the contours of the cyst 



