1198 Wisconsin Academy of Sciences , Arts, and Letters. 
and of the very interesting field opened up by his explanation 
of the sexuality of the Mucorineae, it was thought possible that 
some internal differences might be found which could be cor¬ 
related with the apparent inherent difference between the two 
strains, or to bring the problem to the point where some such 
correlation might be possible when the more general cytological 
features were known. 
The previous work was carried out on Sporodinia grandis, 
a homothallic form, in which it is a very simple matter to ob¬ 
tain zygospores in abundance with the simplest cultural 
methods. The present work, however, has been done on 
Phycomyces nitens, a heterothallic form, in which certain sec¬ 
ondary factors are relevant to zygospore production. 
I am indebted for my cultures to Dr. R. A. Harper, who 
kindly supplied me with zygosporic plates in which the two 
strains had been contrasted and a line of zygospores had re¬ 
sulted in the characteristic fashion where the mycelia of the 
two strains had come together. Isolations were made from 
these plates and the pure plus and minus strains resolved. 
Mixed cultures were also obtained which produced zygospores 
profusely. 
I am also indebted to Dr. L. 0. Kunkel for pure plus and 
minus cultures of Phycomyces nitens which were, I believe, ofi 
the same stock as those furnished in plate form by Dr. Harper. 
METHODS 
Stock cultures of the pure plus and minus strains of 
Phycomyces nitens have been kept on various media. Rice or 
rye bread has been used for the most part because of the ease 
of manipulation. Small Erlenmeyer flasks are very satisfac¬ 
tory containers for culture work because there is less surface 
exposed for evaporation and they are less subject to contam¬ 
ination than the wider-mouthed culture dishes that are ordin¬ 
arily employed. The cotton plugs may be covered with tin 
foil so that all the moisture is conserved. 
At intervals the strains have been inoculated side by side 
on the various kinds of media and in almost every case a line 
of zygospores has been evident by the end of a week. Trans¬ 
fers of individual sporangia have been made, one from each 
strain, with the same marked results when grown together. 
