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Morphologie, Cytologie, Entwicklungsgeschichte 
1. Polyphagus Euglenae is one of the few Chytridiaceae in which 
there is pronounced sexuality. Reproduction takes place by the production 
of zoospores in sporangia, which may be formed on the ordinary vegetative 
cells, or on cysts, or on the sexually produced zygotes. 
2. The organism is parasitic on Euglena viridis. The thallus is 
unicellular and uninucleate, and is provided with delicate pseudopodia which 
penetrate the cells of the Euglenae and bring about complete disintegration 
of their contents. A single thallus may be in contact with as many as 
fifty Euglenae. 
3. The zoospore possesses a single flagellum, at the base of which 
is a yellow oil-drop in close contact with the nucleus. The nucleus is 
surrounded by a deeply stained chromidial mass, which extends also 
around the oil-drop to the point of attachment of the flagellum. It is 
suggested that the yellow-coloured oil-drop may be functional in connexion 
with the phototaxis of the zoospores. 
4. The nucleus of the vegetative cell contains a large chromatin 
nucleolus, which is frequently arc-shaped and is in close contact with a 
lightly stainable nucleoplasm. The nucleus is surrounded on all sides by 
a deeply stained mass of chromidia. 
5. The zygotes are formed by the fusion of uninucleate gametes 
which are equivalent to vegetative cells. They are placed in contact with 
each other by means of a copulating tube which is put out from the 
smaller or male cell and comes into contact with the larger, female cell. 
The apex of the copulating tube swells up and becomes the zygote. The 
contents of the male tube first pass into it, then the contents of the 
female cell. 
6. The two sexual nuclei in the young zygote are at first unequal 
in size, but the smaller male nucleus grows, probably at the expense of 
nourishment brought in from the female cell, until it becomes equal in 
size to the female nucleus. Large quantities of chromatin are then 
extruded from the two nuclei to form two masses of chromidia which 
fuse and form a large granular mass for which the term ‘chromidiosphere' 
(or •chromidiocentrum’) is suggested. The significance of the chromidia 
and the chromidial fusion is briefly discussed. 
7. The germination of the zygote has been followed in detail both in living 
and stained specimens. It was observed to take place in November, five 
months after the formation of the zygotes. The outer spiny coat is ruptured 
and a delicate protuberance appears which develops into a zoosporangium 
similar to the ordinary asexual sporangium, except that it is usually much 
smaller. The two sexual nuclei do not fuse until after their entry into 
the sporangium. 
8. Nuclear division takes place only in the sporangia, never in the 
vegetative cells, cysts or zygotes. The process has been followed in the 
asexual sporangia. The spindle is internal; the nuclear wall breaks down 
first at the poles, where kinoplasmic substance with radiating striae appear. 
The prophases and anaphases of division appear to be those of normal 
mitosis, but, compared with the large amount of chromatin in the resting 
material, the chromosomes are small. 
9. With the exception of Olpidiopsis and Olpidium , the cytology of 
the Chytridiaceae is not very completety known and there are many 
accounts of curious abnormal nuclear phenomena, especially in Synchytrium , 
