Baird—History of Phycomyces Nitens (Agardh) Kunze. 365 
tion of the chromatin in rapidly growing mycelium, I consider the 
vesicle a vacuole, and each portion of chromatin at its periphery a 
nucleus. 
The nuclei that have been thus formed are destined soon to be¬ 
come disassociated from one another and in subsequent nuclear 
division give rise to daughter nuclei by a similar process. 
There appear to be two different forces that bring about the ulti¬ 
mate separation of the daughter nuclei. One is the growth of the 
vacuole from within as just described. The other force is the 
streaming of the protoplasm within the hyphae, giving rise to elon¬ 
gated division figures and most frequently observed in the hyphae 
of the substratum where their tubular form is not uniform in out¬ 
line and very angular in contour. In such hyphae of living cul¬ 
tures I have frequently observed that the rate of streaming is not 
uniform throughout a given diameter. This character of the 
streaming evidently accounts for the fact that the vesicular divi¬ 
sion figures are sometimes elongated and often curved in the 
hyphae of the substratum (figs. 2c, 2d). 
Where the enlargement of the vacuole alone is operating, the 
daughter chromatin masses and the vacuole with which they are 
associated present a spherical figure (figs. 2a, 2e). While the out¬ 
line of the vacuole is still unobliterated, one often finds the daugh¬ 
ter nuclei beginning a subsequent division (fig. 2e). In this figure 
the daughter nuclei have lagged behind the progress of the vacuolar 
membrane and appear within the space bounded by the membrane 
that was carrying them apart. Here, too, the original vacuolar 
membrane is losing its identity and becoming thickened and evi¬ 
dently is about to be incorporated into the slimy portion of the 
cytoplasm. It is also observed that slimy cytoplasm is being 
formed within the cavity of the vacuole between the daughter 
nuclei. 
In the sporangiophore and sporange one does not usually find 
division figures of the nucleus elongated or otherwise distorted, 
for evidently the protoplasm in which the nuclei are imbedded is 
moving uniformly or is at rest, as is the condition of the protoplasm 
of the sporange and sporangiophore as the sporange reaches ma¬ 
turity. In these structures, therefore, one usually finds the nuclei 
associated with approximately spherical vacuoles (figs. 3a and 3b). 
Figures of similar form are also found in the gametes, suspensors, 
and immature zygospores. 
