1214 Wisconsin Academy of Sciences, Arts, and Letters. 
nitens are essentially the same as those that occur in Sporodinia 
grandis . The conditions of nuclear fusions and subsequent dis¬ 
integrations are the same. There appear, in both forms, cer¬ 
tain plastid-like bodies which are associated with the oil which 
occurs as a reserve substance. In Sporodinia the disintegration 
of the nuclei results in the formation of an irregular knotted 
mass of material which in Phycomyces appears as a mass of 
what is probably either nucleic acid or nucleo-protein substance. 
Careful cytological studies of the plus and minus strains of 
germinating spores, young sporangiophores, sporangia and 
progametes have revealed nothing in the nature of a morpholo¬ 
gical sexual differentiation. The author is satisfied that if any 
such means of differentiation between the two strains is to be 
found, it must be looked for in the germ sporangia where se¬ 
gregation undoubtedly occurs or more likely in physiological 
conditions. Perhaps microchemical tests will reveal a differ¬ 
ence in the materials present in the two strains, especially in the 
progametes. 
Many workers have described coenocentra in the Phycomy- 
cetes and McCormick (1912) has described the presence of a 
coenoeentrum in the zygospores of Rhizopus nigricans but in 
Phycomyces nitens nothing has been encountered which answers 
the descriptions of a coenoeentrum. While aggregations of 
nuclei occur, they are entirely independent of any coenocentra- 
like structures. 
Young and partially mature zygospores have been studied in 
Rhizopus nigricans, another heterothallic form, and much the 
same set of conditions has been found as described in the pres¬ 
ent paper. The nuclei show the same clustered condition and 
subsequent nuclear disintegrations occur. The nature of the 
reserve substances in the mature zygospores has not been de¬ 
termined as yet. Work on Zygorhynchus moelleri was aban¬ 
doned temporarily because of the very small size of the zygo¬ 
spores and the accompanying difficulties of technic. But, in 
view of the present work, there remains open an interesting 
problem in connection with such forms as show a morphological 
differentiation between the two sexual branches. It is interest¬ 
ing to note, as Blakeslee has pointed out, that in the heterothallic 
forms where we should expect to find an inequality of the 
gametes none occurs uniformly, while in Zygorhynchus and 
