40(5 
The Schizogregarines 
a Coccidian, and is, indeed, intermediate in this feature between 
anisogamous Gregarines and the strict Coccidia. In most of the Schizo¬ 
gregarines the gametes are isogamous. Schaudinnella more nearly re¬ 
sembles the Coccidia in the particular characteristic (gamete formation) 
in which the majority of the Schizogregarines (leaving out Aggregata 
on which further information is required) differ from the Coccidia. 
Schaudinnella probably resembles a primitive type connecting the 
Gregarines and the Coccidia, devoid of schizogony (a differentiation 
evolved for the purpose of auto-infection of the host), ygt already 
possessing the well differentiated gametes, characteristic of the Coccidia. 
From an ancestral, plastic form resembling Schaudinnella, the Eugre- 
garines appear to have evolved on the one hand, and the Schizogregarines 
and Coccidia on the other; or perhaps, more correctly,the Schizogregarines 
(by acquiring schizogony) have evolved from the Eugregariniform type 
in the direction of the Coccidia. Aggregata would seem to link up 
the isogamous Schizogregarines and the anisogamous Coccidia. 
Probably many other members of the Schizogregarines have yet to 
be discovered. It is possible that some of the Gregarines at present 
only known in the trophozoite phase may yet prove to have schizogonic 
stages, and their sporogony may occur at a strictly limited period of the 
year (see p. 390). There is here a wide field for research. 
In conclusion it may be noted that the life-history of the 
Schizogregarines has a direct bearing on the advisability of retaining 
the separation of the Sporozoa into the Telosporidia and Neosporidia 
of Schaudinn, according as the reproductive phase of the life-cycle 
occurs at the end of or during the trophic or growing period. 
The Ophryocystidae and Schizocystidae increase in volume during 
schizogony, and on this account would be placed in the Neosporidia, 
and not in the Telosporidia along with the Eugregarinae. Such a 
separation of the Schizogregarines and Eugregarines would be un¬ 
fortunate, and scientifically unsound. Again, the Microsporidia are 
now placed among the Neosporidia , but they do not sporulate until 
they have completed their growth, which is a Telosporidian character. 
This is pointed out by Leger and Duboscq (1908, p. 101, footnote). 
It seems preferable, then, to divide the Sporozoa, following 
Metchnikoff and Mesnil, into (a) Ectospora, wherein the spore-mother- 
cells or sporoblasts are formed at the periphery of the gametocyte, 
and (ft) Endospora, in which the spore formation occurs in the interior 
of the body of the trophozoite, the spore-mother-cell or pansporoblast 
being separated off internally. The Schizogregarinae would then be 
