242 
Critliidia pidicis n. sp. 
tlagellates, and thei’e seems to be a tendency for their number to 
increase just prior to division. As at this time the organism is passing 
through a critical period, the migration outwards of chromidia may be 
an adaptation to secure a more perfect equilibrium between the general 
cytoplasm and the nuclear elements. 
One of the most noticeable features about G. puUcis is the beauty of 
its membrane. The undulating membrane is large and well marked. 
Its chromatic border is highly retractile in life, and stained specimens 
show it as a well-marked chromatin containing edge to the membrane 
(figs. 15-17), continued outwards just beyond the body as the free 
flagellum. Contractile myonemes (figs. 13, 15, 16, 17) are present in 
the membrane and faint body myonemes (figs. 9, 16) are also seen 
occasionally. The free flagellum and the chromatic border of the 
membrane show a transverse striation in a few cases. There is much 
morphological variation among the full-grown flagellates, depending on 
the frequency of and variation in division. 
The Post-flagellate Stage. 
The post-flagellates of G. pidicis (flgs. 23-36) again show differ¬ 
ences from most other Grithidia. In the majority of these organisms 
division into four without subsequent growth seems to be a common 
procedure prior to the formation of post-flagellates. In G. pulicis 
division into two, followed by some slight amount of growth seems 
general. But as flagellates of different sizes may divide, the range of 
size of the cysts is fairly great. The fully formed post-flagellate is from 
S /j, to 6 yu. long and from 2'0 p to 4'6 p broad in those that I have 
examined. The processes leading up to the fidl post-flagellate stage 
may be herewith summarised. Retraction of protoplasm from both 
ends of the organism towards the nucleus occurs (figs. 23-25); part 
of the protoplasm is absorbed. The chromatin constituent of the 
membrane appears to be absorbed and the free flagellum shortens 
(flgs. 23-28). General fusion of membrane and body occurs and the 
organism becomes ovoid (figs. 29-36). A thin, gelatinous secretion 
appears on the outside of the ovoid ma.ss and hardens into a varnish¬ 
like cyst wall around the contents. The fully formed post-flagellate 
(figs. 29-36) consists then of a thin coat enclosing the nucleus and 
blepharoplast together with a fair amount of protoplasm. The nucleus 
is often round but it may be oval. As a rule, the nucleus and 
blepharoplast remain quite distinct and slightly separated one from 
