Some recent work on the cytology of fungus reproduction 
203 
lies near the coenocentrum and increases in size. The single male nucleus 
passes over together with some protoplasm and fuses with the female 
nucleus. The oospore is uninucleate. 
This account is quite in accord with what has been described in 
the other Saprolegniineae. In all recent work the sexual organs are 
described as being multinucleate at first: all the nuclei degenerate except 
one male nucleus and one female nucleus. These fuse in the oosphere. 
No series has yet been found which corresponds with that discovered in 
the Peronosporineae, e. g. in Albugo, where a regular transition can be 
traced from multinucleate antheridium and oogonium, the nuclei of which 
fuse together in pairs, to a case where all the nuclei degenerate with 
the exception of one male and one female nucleus, which then fuse. Also 
in the Saprolegniineae (with the exception of the anomalous Pythium) 
there is no periplasm formed as in the Peronosporineae. The only questions 
which seem to be debatable are (1) whether the body in the oosphere is 
a coenocentrum and equivalent to the similar structure found in the 
Peronosporineae, at least physiologically (Davis and Kasanowsky), or 
whether it is a centrosome with, or without, additional., structures (Trow, 
Claussen and Mücke); (2) whether two mitotic divisions take place in 
the sexual organs, as Trow states. Trow thinks that in Achlya de Bary- 
anum he has seen two divisions which constitute a true reduction division, 
the number of chromosomes being halved during the process. Two divisions 
have been observed in the sexual organs of several of the Peronosporineae 
e. g. Albugo Bliti, but it is not known whether this is usual: indeed various 
observers have differed in their accounts of the same species. It seems 
extremely doubtful that the two divisions observed constitute a reduction 
division, as Davis (1903), working on a form of Saprolegnia monoica, 
which was without antheridia, observed a division in the oogonium. 
Another section of the group, the Mucorineae have been rather 
neglected from a cytological standpoint although their morphology and 
physiology is probably better known than that of any other fungi. The 
meagre cytological results are all at variance. The isogamous species 
(which are at the same time homothallic) were the first investigated. 
Sporodinia grandis, because of the ease by which its zygospores can be 
obtained, is the species which has been most studied. It is hardly a 
suitable species however, because of the large number of small nuclei in 
the gametes and the presence of oil globules, and mucorine crystals. 
Dangeard and Léger (1894) first showed that the young zygospore was 
multinucleate. Léger (1895/96) continued the work and extended his 
researches to many other genera. The zygospores of Sporodinia grandis 
and Mucor mucedo were particularly studied. Léger stated that in the 
zygospores the nuclei gradually disappear. At the precise moment of 
disappearance two groups of small spheres („sphères embryogenes“) pro¬ 
bably arising from the union of a certain number of nuclei appear. At a 
later stage all the spheres of each group fuse forming the notorious 
„sphères embryonnaires“. At germination these spheres fuse. 
Dangeard immediately dissociated himself from Légers work. 
Gruber (1901) examined Sporodinia. He found numerous nuclei which 
were at first more numerous in the parietal layer but afterwards were 
evenly dispersed. He found neither degeneration of nuclei nor fusion of 
nuclei although he assumed that the latter probably occurred. 
