404 
Tli e Sell izogregarines 
all the points, noted in the foregoing paragraph, into consideration, 
it seems to me that Aggregata stands apart from the rest of the group 
in being heteroic. This fact is not obvious in Leger and Duboscq’s 
classification, and the mode of sporulation, on which they base their 
classification, can be easily explained (see p. 382). The method of 
sporulation does not seem to me to be of so much importance as 
the heteroic character of Aggregata, especially when it is remembered 
that the presence of extracellular schizogony brings Opliryocystis and 
Schizocystis into contiguity. 
Table showing the position of the Schizogregarinae in 
the Order Gregarinida. 
Sub-order: Schizogregarinae— Gregarines with a schizogonic phase in 
their life-cycle. 
Section I — Homoica —Schizogregarines whose complete life-cycle 
takes place in a single host. 
Sub-section (a) Ectoschiza —With schizont extracellular. 
Opliryocystidae, with a single sporocyst. 
e.g. Opliryocystis. 
(?) Eleutheroschizon (sporogony unknown). 
Schizocystidae, with numerous sporocysts. 
e.g. Schizocystis. 
(?) Siedleckia (sporogony unknown). 
Sub-section (/3) Endoschiza —With schizont intracellular. 
Selenidiidae, with longitudinal myonemes the whole 
length of the body, 
e.g. Selenidium. 
Merogregarinidae, with longitudinal myonemes confined 
to the anterior (pre-nuclear) region, 
e.g. Merogregarina. 
Section II— Heteroica —Schizogregarines whose life-history is 
divided between two hosts, with schizogony in the one, 
sporogony in the other. 
A ggregatidae, in crabs and cephalopods. 
e.g. Aggregata. 
The Schizogregarines may therefore be conveniently divided into 
forms whose life-cycle is completed in one host, i.e. homoie forms, in 
contradistinction to the heteroic Aggregata. Among the homoie forms 
