THE STRUCTURE AND BEHAVIOR OF THE NUCLEUS IN 
THE LIFE HISTORY OF PHYCOMYCES NITENS 
(AOARDH) KUNZE AND RHIZOPUS 
NIGRICANS EHRBG 
E. A. Baird 
Among the contributions to various phases of the life history 
of the Mucoraceae, a number of the writers do not include any 
clear statement of the structure of the nucleus or how it behaves 
in division. Most of the workers, who have attempted to follow 
closely the behavior and structure of the nucleus in zygospore 
formation, have described the resting nucleus in the forms studied 
as consisting of a nucleole, a nucleoplasm containing little or no 
stainable substance, and a nuclear membrane. In the consideration 
of nuclear division they have generally described a type of mitosis 
with a spindle formation, but in the details of this process the 
descriptions are incomplete. Many of these have described numer¬ 
ous nuclear fusions during the maturation of the zygospore together 
with a disorganization of other nuclei that do not fuse. 
Dangeard and Leger (1894a) in a cytologieal study of zygospore 
formation in Sporodinia grandis and two species of Mucor have 
described the structure of the nucleus in the vegetative hyphae and 
the sexual branches of these forms as vesicular, consisting of a 
surrounding membrane and a centrally placed nucleole, which 
are separated by a non-staining ‘‘cytoplasm” containing a little 
chromatin. In the young zygospores of these forms they find two 
sizes of nuclei. 
In another report, Dangeard and Leger (1894b) describe with¬ 
out figure the structure of the nuclei in Mucor mucedo and M. 
racemosus as similar to that described above. In the ripe zygo¬ 
spore of Sporodinia the small and, later, the large nuclei disappear. 
After their disappearance the zygospore contains a varying num¬ 
ber of deep-staining bodies. 
Leger (1895a) figures the nucleus of the vegetative mycelium 
as a vesicular body with a centrally placed nucleole. He describes 
