184 
Wager. — The Life-history and 
scattered in the cytoplasm of the zygote during the early stages of develop- 
ment, which Dangeard (’00) calls coenospheres, must also be regarded 
as chromidia, and it is interesting to find that Dangeard considers that 
they are of a fatty nature. The chromidia of Polyphagus are strictly 
comparable to the granular mass which occurs in the oospores of Cystopus 
and Peronospora, the so-called coenocentrum. 
The function of the coenocentrum is not clearly understood. When 
first discovered, I thought its purpose was to act as a kind of attractive 
centre to bring the two sexual nuclei together in the middle of the zygote. 
This view has generally been accepted, but from recent investigations I am 
not satisfied that it is the correct one. It appears to be much more nearly 
concerned with the vegetative activities of the oospore than with the fusion 
of the nuclei, and although it may not actually possess the characteristics of 
a fatty body, as Dangeard suggests (’00), it certainly seems to be the centre 
of formation of the oily reserves which accumulate in the oospore. The 
granules of which it is composed are probably extruded from the oogonial 
nuclei and should therefore, in the present state of our knowledge, be 
classed as chromidia. 
When the chromidia are grouped together into a well-defined mass 
in the cell, as above described, the term chromidiosphere (or chromidio- 
centrum) may perhaps be used instead of coenocentrum. 
Chromidial Fusion. 
Chromidia as definite structural organs in the cell are of frequent 
occurrence in the Protozoa, and it is interesting to find them so well marked 
in Polyphagus and presenting such close resemblances to the chromidial 
masses of the Protozoa. Some of the figures of chromidia in Pelomyxa 
given by Bott (’07), for example, resemble to an extraordinary degree those 
which I have given of Polyphagus. The fusion of chromidia in the zygote 
of Polyphagus also resembles in many respects that which takes place 
in many Protozoa, but it is of a much simpler type. In the Protozoa 
the fusion of the chromidia, or chromidiogamy, as it is sometimes called, is 
one of the stages in a complex nuclear cycle during which the original 
nuclei degenerate and new ones are reconstructed out of the chromidia. 
In Difflugia urceolata, for example, the two sexual cells each with nucleus 
and chromidia come into contact and the contents of one pass into the 
other. The chromidia then fuse and the nuclei ultimately degenerate, new 
nuclei being formed from the chromidial mass. Again, in A rcella (see 
Minchin, p. 148 ) each of the fusing cells contains a nucleus and chromidia. 
The contents of one cell pass into the other and the primary nuclei 
degenerate, then ‘ break up into a fine dust of chromatin particles and 
become intimately commingled ’. ‘ When this process is complete, the 
protoplasm with the chromidia becomes again distributed between the two 
