GAMKTIC MEIOSIS IN MONOCYSTIS. 387 



be easily identified and we often find another species which might 

 be regarded as one of the varieties of Monocystis lumbrici which 

 are not precisely described in the literature. 



Cuenot (1901) Brasil (1905) and Hesse (1909) all remark on the 

 difficulty of tracing a pair of pseudo-con jugants of Monocystis 

 back to the individual agamonts which form the subjects of the 

 specific descriptions. Where only one type of gregarine is present 

 in an organ the assumption is safe that the cysts found in the 

 organ come from that one type. When, however, there may be 

 as many as five different species present at the same time, as is 

 the case in the seminal vesicles of Lumbricus terrestris, then the 

 problem is real. There is indeed a real danger of confusing 

 sporocysts from different species and of getting a false interpre- 

 tation of the life history of any one. On the other hand, if the 

 species of Monocystis were based upon the size and structure of 

 the sporocysts and sporoblasts instead of upon the agamont 

 stages the difficulties of identification attendant upon multiple 

 infection would be materially lessened. 



While an ideal condition would be the indisputable association 

 of a given agamont with its definitive sporocyst in these mono- 

 cystids, for our purpose such an ideal is unnecessary. In all 

 gregarines two individuals upon reaching maturity become 

 associated in pairs (pseudo-conjugation) and a capsule, called the 

 sporocyst capsule or simply sporocyst, is formed about them 

 (Fig. i). These gamonts then proceed to form gametes by 

 repeated divisions of the originally single nucleus in each, the 

 gametes ultimately appearing as a zone of small nucleated cells 

 budded out from the periphery of the gamonts. The gametes 

 from one parent cell then meet and fuse with the gametes from 

 the associated cell. The zygotes thus formed by fusion two by 

 two are practically equal in number to the total number of 

 gametes formed by either one of the associated parent cells. 

 Each zygote forms its individual capsule termed the sporoblast 

 capsule within which the zygote nucleus, an amphinucleus, 

 divides a certain number of times, usually three. The eight 

 resulting nuclei become the nuclei of the definitive germs termed 

 sporozoites. 



It is no more difficult to recognize different specimens of the 



