H. 13. Fantham 
391 
anterior region (Fig. 8, A, B, my), stretching from the epimerite to the 
neighbourhood of the nucleus in a fan-like manner. The nucleus is 
large and well-marked. It is vesicular, with a large karyosome 
(Fig. 8, A, ley ) lying in a faint, chromatic reticulum. The karyosome 
may be spherical, notched or dumb-bell shaped (Fig. 8, B). One or 
more plasmosomes are frequently to be seen lying in the nuclear sap. 
There is a definite nuclear membrane with an irregular lining of 
chromatin internally. 
The asexual cycle, or endogenous multiplication, is completely known. 
Schizonts occur within the gut epithelium of the Ascidian host. These 
schizonts are about 17/a long by IO'o/a broad. When they have attained 
this size the schizonts begin to sporulate. The nucleus of a schizont 
divides into 8 to 18 fragments of chromatin, there being no remains 
of the parent nucleus. The daughter nuclei are distributed fairly 
evenly throughout the mother cell (schizont). The cytoplasm of the 
latter collects around each daughter nucleus and so a small, but 
apparently inconstant, number of merozoites is formed (Fig. 8, C). 
These separate and find their way into the lumen of the gut and so 
account for auto-infection of the host. 
Sporogony is also known, though somewhat incompletely. Two 
fully-formed trophozoites or gametocytes come together, associate and 
encyst. Finally sporocysts 14/a by 11/a are seen (Fig. 8, D). The 
sporocysts are oval and contain eight small sporozoites (Fig. 8, E) 
arranged “en bardlet.” These sporozoites serve for cross-infection. 
Merogregarina reacts on its host, for trophozoites, while still in the 
gut lumen, are seen lying in bays or depressions in the epithelium of 
the gut. The effect of the schizont is, of course, more marked, and is 
of the usual character associated with intracellular schizonts. 
Merogregarina is considered to be nearest the Selenidiidae in 
affinities, though it has octozoic spores, and the myonemes are only seen 
in the anterior region of the trophozoite. 
This most interesting parasite, M. amaroucii, extends the distribution 
of the Schizogregarines to the Protochordata. It is also of interest to 
note that Merogregarina harbours a Chytridiopsis-like parasite within 
its protoplasm 1 . In this respect it resembles various Selenidiidae, as 
described by Brasil and Fantham, Caullery and Mesnil, and Leger 
(noted on p. 389). 
1 For further details see Porter (1908); a complete paper, fully illustrated, will appear 
in due course. 
Parasitology i 
25 
