H. B. Fantham 
379 
In this diagram m refers to the variable number of merozoites 
formed from a schizont. Similarly, n refers to the large number of 
gametes formed from each gametocyte. 
Each spore usually contains eight sporozoites. 
The following points should be considered in connection with the 
above generalised diagram of the life-cycle: 
Four sporozoites are present in Selenidium (e.g. S. echinatum), 
according to Caullery and Mesnil (see Fig. 2, E). 
Intracellular schizogony prevails in Selenidium and Merogregarina. 
Extracellular schizogony occurs in Ophryocystis and Schizocystis. 
Nuclear reduction, so that one spore only is formed, takes place in 
Ophryocystis, this being expi’essed by the formula n = 1 (see Fig. 4, D). 
In the Aggregatidae, the schizogony takes place in one host (Crab), 
and the sporogony in another (Cephalopod Mollusc). 
The number of sporozoites in the spore varies in the different 
species of Aggregata (e.g. 3, 4, 8, 16, 24). 
VI. Detailed Morphologies and Life-Histories. 
The Schizogregarines at present comprise five well-marked families: 
Ophryocystidae, Schizocystidae, Selenidiidae, Merogregarinidae and Ag¬ 
gregatidae. The morphology and life-history of members of each of 
these families may now be set forth in some detail, avoiding, as far as 
possible, repetition of what has been written in the preceding section. 
It will be most convenient to consider these matters under the headings 
of the generic names, excepting in the case of the Selenidiidae. 
(1) Genus Ophryocystis. 
Regarding the genus Ophryocystis Schneider, an account of the 
life-cycle of which has already been given, the following further points 
are of importance. 
The presence of cytoplasmic processes or fixative filaments in the 
extracellular or trophic forms is not entirely without parallel in the 
Eugregarines, for in the genus Pterocephalus (Schneider), a Eugregarine 
from the digestive tract of Scolopendra cingulata, similar processes of 
a fixative nature are known, proceeding from the epimerite region of 
the trophozoite of Pterocephalus into the cells of the epithelium of the 
gut of the host. In Ophryocystis the various forms of trophozoite or 
