676 DR. H. B. FAXTiiAM ON TUE [May 3, 



of the karyosome, however, is not centrally fixed ; it may lie to 

 one side of tlie nucleus (figs. 8, 10). 



The growth of the trophozoite naturally aflfects that of the host- 

 cell. The proto]ilasm of the latter becomes moi-e and more 

 tenuous, great hypertrophy of the host-cell occurring. This 

 condition is maintained for some time and finally a limit is 

 reached and atrophy sets in, the nucleus of the host-cell then 

 appearing as a small, often crescentic mass (figs. 10, 14) to one 

 side of the film (fig. 12) that represents the host-cell. A clear 

 space often intervenes between the parasite and the enveloping 

 epithelial film (figs. 9, 11, 12). 



The trophozoite, having attained its full size (some 10/^ to 12 fx 

 in diameter) within the host-cell, proceeds to divide, and the 

 result of its division is to increase the number of parasites within 

 the host. This stage in the existence of Elmeria avutm is known 

 as the schizont (agamont), and the method of multiplication is 

 termed schizogony. 



(b) Schizogony. 



The schizont (fig. 12) is a more or less spherical parasite. At 

 first it is uninucleate (fig. 12«), but soon its nucleus begins to 

 fragment (fig. 12 h). The division of the nucleus of the schizont 

 is of the natui'e of multiple fragmentation rather than of a series 

 of binary fissions of the nucleus and karyosome (figs. 13-18). 

 The parasite is very small and it is not easy to iFollow the 

 cytological details, even under the best and highest powers of 

 magnification. Some of the poi'tions of chromatin iai midtiple 

 fragmentation may sometimes appear connected by thin strands 

 (fig. 13) for a shoi't period, but the fragments soon tiavel to 

 the periphery of the schizont. The small daughter masses of 

 chromatin, at fiist homogeneous, gradually show difterentiation, 

 becoming minutely vesicular with a dot of chromatin usually to 

 one side (figs. 14-16), but occasionally central. Thus the nuclei 

 of the future merozoites are forming their karyosomes early. 



The daughter nuclei having migiated to the periphery of the 

 mothei- cell (fig. 16), the cytoplasm of the schizont concentrates 

 around them forming sn)all ovoid masses (figs. 18, 19). The 

 daughter forms so produced are the mei'ozoites (agametes) which 

 measure 6u to 1 0/x. in length. They gradually acquire a vermiform 

 shape and arrange theuiselves around the remains of the proto- 

 plasm of the mother cell like the segments of an orange or the 

 staves of a barrel (PI. LV. figs. 20-22, PI. LVI. figs. 23, 24). 

 Owing to this method of grouping, the merozoites are said to be 

 arranged "en barillet." The groups, when ripe, soon break up 

 and the individual mei'ozoites are liberated. The movements of 

 the merozoites, when free, x-eseinble those of the sporozoites. 



The number of merozoites foimed from a single schizont seems 

 to vary. Eight to fourteen seem to be common numbers, but as 

 many as twenty have been found. 



The merozoites finally are slightly curved vermicules (PI. LVI. 

 figs. 23, 24), po.^.se.ssiui: a niu-1eus which may lie apjiroximatcly 



