Baird—History of Phycornyces Nitens (Agardh) Kunze. 367 
evidently from one of the nuclei, and in this group each has begun 
to form a vacuole. 
After the fusion of the gametes and during the growth of the re¬ 
sulting zygospore, I find no evidence of a pairing or fusing of the 
nuclei. During the growth of the zygospore, nuclear division 
occurs continuously until the protoplasm finally takes on its resting 
condition as described below. All of the nuclear division figures 
of the zygospore are of the spherical type. The only observed 
change in the protoplasm after the fusion of the gametes is the 
increased affinity of the cytoplasm for the safranin and gentian 
stains. As a result of this change in staining reaction, the differ¬ 
entiation of the nuclei is not as definite in the zygote as in the sus- 
pensors or the vegetative hyphae. The nuclear division figures of 
the zygospore are of the same form as has been described for them 
in the sporange (figs. 5a-5e). Figure 5 represents a zygospore 
during the growing period while the exospore is being formed and 
shows the fragments of the walls of the gametes which fused to 
form the first wall of the zygospore. 
During the growing period of the zygospore many of the divid¬ 
ing nuclei are found in groups of four to eight. In figure 5a six 
dividing nuclei of such a group, at the same optical level, are 
shown in their relative positions. Evidently these have originated 
from the same nucleus through two successive divisions, but, since 
the vacuoles bringing about the divisions have enlarged but little, 
the daughter nuclei of each division remain in close proximity to 
each other. On the other hand, the isolation of other daughter 
nuclei in the zygospore is accounted for by the greater expansion 
of the vacuole separating the nuclei. Figure 5b contains both 
isolated and grouped nuclei. 
The nuclei of a zygospore which has attained nearly its full size 
are found associated with smaller vacuoles than are the nuclei of 
a zygospore during the rapidly growing period, or of the vegetative 
hyphae. Compare figures 5c and 5e of a full-grown zygospore with 
figures 3a and 3b from a sporange, and with figures 6a and 6b from 
a growing zygospore. 
In the stained preparation of the protoplasm I have found no 
evidence of fat, nor structures identified with its formation. How¬ 
ever, a test with Sudan III of protoplasm crushed out' of zygospores 
in all stages of development shows very clearly the presence of fat. 
Undoubtedly the fat in the zygospores occupies many of the larger 
spaces that appear as vacuoles in the preparations. The fat is 
