Some recent work on the cytology of fungus reproduction, II 
223 
than the female nucleus and contains less chromatin. The two nuclei come 
together in the zygote and the male nucleus grows until it is almost exactly 
similar in size to the female nucleus. The two nuclei then move apart to 
opposite sides of the cell and extrude chromidia, a more or less distinct group 
being formed by each. Shortly after their appearance these chromidial masses 
fuse together and form a “chromidiosphere” or “chromidiocentrum” in the centre 
of the cell. Fusion of the generative nuclei does not occur until the contents 
of the zygote pass into the sporangium. It is only in the sporangium 
that nuclear division occurs. The divisions have been studied in the 
asexual sporangia though the first division was not observed. The spindle 
is internal. The chromosomes number about ten or twelve and are very 
minute only a small amount of the chromatin mass being used up. The 
nuclear wall breaks down at the poles and centrosome-like structures 
become visible. The prophases and anaphases appear to be those of 
normal mitosis. Wager thinks that Polyphagus shows relationships with 
the Mucoraceae and the other Oomycetes and with the Protozoa, and 
that the chromidial fusion and the later nuclear fusion “may afford some 
clue to the explanation of the delayed nuclear fusions and double nuclear 
fusions observed in the higher Fungi”. 
Griggs (1912) has worked at Rhodochytrium Spilanthidis which 
“seems to occupy a transitional position between the protococcoid algae 
[such as Phyllobium] and some of the chytridiaceous fungi. ... It has 
no chlorophyll and is strictly parasitic in its mode of life. . . . Although 
entirely incapable of photosynthesis, it develops abundant starch. But the 
starch grains are apparently built up directly in the cytoplasm, for neither 
plastids nor pyrenoids have been found” — a “paradoxical combination 
of characters”. The plant has more or less of red pigment in all its 
stages. In both resting cysts and zoosporangia there is an extensive 
system of haustorial rhizoids proceeding from the basal portion. The 
two are distinct from the very beginning but their nuclei undergo the 
same development which, in the case of the resting spore leads to a 
remarkable, but seemingly universal and perfectly normal shriveling pre¬ 
paratory to the long dormant period, and in the zoosporangium to mitosis. 
At the end of the vegetative activity of the - resting spore the rhizoids 
are ultimately cut off by cell walls and the mature spore has a two 
layered cellulose exospore and a thick non-cellulose endospore. On the 
beginning of germination in the spring, the nuclei again become turgid 
though they are apparently smaller than before shriveling up. In the 
later developmental stages of the zoosporangia there is always one large 
vacuole which occupies the upper half of the cyst. The latter reaches its 
full size before there is any indication of nuclear division, but when this 
commences the stages follow each other in rapid succession until a large 
but variable number of nuclei have been formed. Then segmentation 
occurs which appears to be brought about by the precipitation of mem¬ 
branes around the protospores which quickly round off and ultimately 
give rise to zoospores. These frequently contain starch grains, but are 
colourless except for the red anterior end. They possess two anterior 
cilia which are of a more highly type than those of the Chytridiales. 
The zoospores correspond in every important particular save in the 
absence of chlorophyll with algal zoospores in general. They are uni¬ 
nucleate and there is a deeply staining body at the base of the cilia 
