Some recent work on the cytology of fungus reproduction, II 
227 
nucleus has a rather large nucleolus and an indefinite structure. The 
nucleus later becomes oblong and thickened at the ends. Preparatory to 
division the nucleus elongates a little, stainable material appears at the 
periphery and “centrosomes’’ at the poles. The nucleolus divides equally 
and the halves place themselves more or less in the longitudinal axis of 
division. A nuclear plate, the structure of which could not be properly 
made out, arises in the equatorial plane. In full grown parasites another 
type of nuclear division occurs. The nucleus appears poor in content, the 
chromosomes can later be relatively clearly made out but the centrosomes 
are scarcely visible. The nucleolus quite disappears. The nuclear mem¬ 
brane is now dissolved, the chromosomes arrange themselves on the 
nuclear plate and the division proceeds quite normally. Besides this first 
division where the chromosomes are rather small there is a second 
division where the chromosomes are large and rod-shaped. Nèmec con¬ 
siders these divisions the first and second “Fortpflanzungsteilungen”, the 
second division sometimes occurring after the cytoplasmic contents are 
segmented. This segmentation was not closely followed. The first formed 
portions apparently divide to give rise to the zoospores. The segments 
contain no typical resting nucleus, but a heap of more or less distinct 
chromosomes. The author thinks the heaps divide. The zoospores are 
uniciliate and possess a small nucleus which has no apparent nucleolus. 
Bodies are also found which surround themselves with a membrane 
and divide into uninucleate portions, whose nucleus at first shows chromo¬ 
somes. The cells secrete a membrane and later round themselves off 
remaining together though the original membrane surrounding the group 
can no longer be seen. Nèmec considers each cell a sporangium and 
the group a sporangial sorus. The sporangia give rise to zoospores. In 
many cases it could be seen that the nucleus as well as the protoplasm 
had divided. In the same cells as the sporangial sori were frequently 
found small uninucleate vegetative parasites. These were a little larger 
than the zoospores and probably arose from them. „Copulation von 
Schwärmsporen wurde nicht beobachtet.“ 
The genus which has received most attention in the Chytridiaceae is 
Synchytrium. Dangeard (1890) recorded that in 5. Taraxaci the large primary 
nucleus divides by ordinary ainitosis. The nuclei sometimes divide mito- 
tically and both methods may occur side by side in the same cytoplasm. 
Rosen (1893) described a direct division of a different type. The chro¬ 
matin loops into a spireme, the nucleolus divides and the halves migrate 
to the forming daughter nuclei. The nucleus then constricts in the middle 
thus completing a division of the nucleus in its spireme condition without 
the aid of the usual achromatic structures. The following divisions take 
on more and more the character of mitosis. F. L. and A. C. Stevens 
(1903) first stated that the primary nucleus in S. decipiens divided mito- 
tically and most observers have confirmed this statement. Striking points 
about the mitosis, are the vacuolisation of the nucleolus and the shortness 
and thickness of the few spindle fibres. According to Griggs (1909) the 
numerous recorded peculiarities occur mostly in a somewhat definite 
“period of irregularities” immediately following the division of the primary 
nucleus. In this stage direct division is more frequent than mitosis and 
takes place by at least two processes: 1. “Nuclear gemmation” where 
the karyosome of the parent nucleus gives off a small karyosome which 
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