368 Wisconsin Academy of Sciences, Arts, and Letters, 
evidently dissolved by xylol or chloroform during the clearing and 
imbedding processes. 
A mature zygospore two weeks old shows very little of the slimy 
portion of the cytoplasm. Figure 7 shows the condition of the 
protoplasm in a zygospore from an eleven-day-old culture, in which 
the zygospores would vary in age from three to seven days. At 
this stage one finds that the protoplasm consists of three distinct 
portions, vacuoles, the slimy portion of the cytoplasm, and nuclei. 
The vacuoles evidently represent spaces filled with oil, cell sap or 
gas. Some of the vacuoles contain a slightly-staining granular 
substance, as has frequently been described by other workers, but 
this is not so specially characteristic of the vacuoles of the zygo¬ 
spore as it is of the vacuoles of the vegetative hyphae. The slimy 
portion of the cytoplasm is still in evidence but in a much reduced 
proportion. Most of the nuclei together with the vacuoles asso¬ 
ciated with them present a different aspect than has been described 
for them heretofore in the life history of the plant. Some of the 
vacuoles associated with the nuclei appear as has been previously 
described; the others now contain a substance that stains with the 
same reaction as do the chromatin bodies at the periphery of the 
vacuoles. It appears that the chromatin substance has increased 
in volume accompanied by a reduction in the proportion of the 
cytoplasm. 
In figure 7a a distinct vacuole is present, but the surrounding 
membrane has become thickened and stains deeper. Figure 7b 
illustrates a nuclear vacuole that has become filled with a stainable 
substance. Figure 7d represents the final stage in the develop¬ 
ment of such a nuclear structure in the mature zygospore, the form 
in which most of the protoplasm, except the fat, is found. These 
structures are often so closely crowded together that their sur¬ 
faces are compressed flat against each other (fig. 7d). During this 
change the same stain-absorbing elements as are contained in the 
chromatin characterize all the material contained in the nuclear 
vacuoles. I call these structures ‘^reserve food bodies”. Each 
consists of a variable amount of food reserve, which occupies the 
space of the nuclear vacuoles, and one or more chromatin masses 
which may usually, though not always, be observed as deeper- 
staining bodies at' the periphery (fig. 7b). 
My interpretation is that during the process of maturation of the 
zygospore there are no nuclear fusions. After the fusion of the 
two gametes the nuclei continue to divide rapidly, as they do in 
