Keene—Studies in Zygospore Formation. 1213 
cytoplasmic balance, it seems improbable that the immense num¬ 
ber of nuclei which are present in the zygospore following the 
fusion of the two gametes, should persist in such a comparatively 
small structure, and nuclear disorganizations might normally be 
expected to occur. 
There occurs an interesting change in the development which 
is of importance from a secondary standpoint only. Following 
the formation of the delimiting walls in the gametophores, there 
appear slight protuberances from the walls of the suspensors 
(PL I, fig. 6). These grow rather rapidly and give rise to the 
peculiar, dichotomously-branched appendages which grow out 
and surround the zygospore givling to it a very characteristic ap¬ 
pearance (fig. 7). These appendages first appear on the same 
suspensor in which septation first occurred. This, however, 
does not appear to be due to any inherent difference between the 
two strains. Internally the changes are interesting. 
Nuclear divisions appear to follow the cutting off of the ter¬ 
minal portions, or the nuclear divisions inaugurated in the 
progametes continue, and there results an increase in the num¬ 
ber of nuclei in the suspensors. In a cross section of the sus¬ 
pensors there appear peculiar deep-staining areas opposite the 
places from which the appendages grow. The nuclei in these 
areas appear as if caught in a current and even show elongation 
in the direction of the current. The appendages as they elong¬ 
ate become filled with protoplasm and later appear vacuolate 
with only a thin lining layer of protoplasm in which the nuclei 
are distributed in about the same proportion as in the vegetative 
mycelium. All the protoplasm and nuclei disappear in the 
older stages and the appendages and suspensors appear empty 
(PI. Ill, fig. 14). Occasionally dense, red-staining bodies may 
be found in the suspensors. They resemble closely the protein 
masses found in the partly mature zygospore and are probably 
of similar origin. 
Zygospore germinations were secured in only one small lot of 
material so it has not been possible to carry the history of the 
internal changes to completion. It will be interesting to know 
what is the fate of these various substances in germination and 
what are the nuclear behaviors which complete the cycle. 
Thus it will be seen that fundamentally, the changes which 
take place when sexual reproduction occurs in Phycomyces 
