THE SPOROZOA 



157 



the formation from the zygotes of the resistent spores, by which 

 the parasite is disseminated (see Fig. 29, p. 185). 



The adult trophozoite, when it is ripe for reproduction, is 

 commonly known as a sporont, but may be better termed a 

 gametocyte, since it gives rise to the gametes. Two gametocytes 

 come together and become very closely apposed to form a spherical 

 body (Fig. 4), the two individuals remaining, however, perfectly 



PlO. 4. 



Association and encystation of 

 Monocystis magnet,, a, a couple 

 attached to the ciliated epithelium 

 of the seminal funnel of the earth- 

 worm. The two gregarines are 

 covered by a furry coat of adherent 

 spermatozoa, b, a couple detached 

 from the seminal funnel and en- 

 veloped by a common cyst-mem- 

 brane. s.f, seminal funnel ; n, 

 nucleus of the parasite ; c.m, double 

 cyst - membrane. (After Cuenot.) 

 a, x37; b, slightly less. 



distinct from one another, each forming one hemisphere of the 

 common mass. This union of the two gametocytes must not be 

 confounded with the true conjugation : the two individuals are 

 merely in association they are keeping company, as it were, as 

 a preliminary to the formation of gametes. The two associated 

 gametocytes, which often exhibit a slow rotatory movement, now 

 become surrounded by a common envelope or cyst (Fig. 4, b, c.m), 

 secreted by them in two layers ; first a rigid external epicyst, then 

 a thin internal endocyst. 1 Meanwhile important changes are going 



1 According to Cecconi [11], in M. ay His the sporonts first become encysted 

 singly, and two such cysts then approach each other and join together. This prob- 

 ably applies only to the first signs of cyst-formation, as two completely encysted 

 gregarines can hardly be suiliciently motile to admit of their travelling towards one 

 another. 



