242 
A. F. Blakeslee, 
Gruber, in the paper already mentioned, states that he investigated 
sectioned material of Z. heterogamus and Z. Moelleri and in addition 
with the latter species followed the process of conjugation in living material 
under the microscope. Consecutive figures showing the development of 
individual zygospores, however, are not given. His figure 1 corresponds 
to our figure 2 and correctly gives an early stage where the more vigo¬ 
rous zygophore has bent around and applied itself to the more delicate 
filament. His figure 2 represents a later stage and resembles in appea¬ 
rance the condition shown by our figures 7, 13 and 22. We shall use 
our figure 22 in explanation of his interpretation. From the delicate 
filament (fig. 22 a), according to his account, a large progamete grows out, 
pushing away the larger zygophore (b) and soon cuts off by a basal cross 
wall a large female gamete (c). At this stage a violent motion of the 
protoplasm in the conjugative apparatus is reported. The writer, however, 
has been unable to discover any decided movement of the living proto¬ 
plasm directly connected with zygospore formation. The swollen end of 
the larger zygophore (b) is considered the male progamete since Gruber 
believes he has found evidence from sectioned material that fertilization 
consists in a squirting in of a mass of protoplasm from b into his female 
gamete (c). The line separating what are really the gametes (m and / 
in our fig. 21), he would hold was usually at least only a partial wall 
showing itself as a temporary ridge inside his female gamete (c). 
Our studies on living and stained material of Z. heterogamus , Z. 
Moelleri, as well as of Z. Vuillemini (which, however, is not figured) 
have convinced us that Gruber has fallen into error in interpreting the 
process of conjugation in the genus Zygorhynchus on account of the 
difficulty usually experienced in following the process in living material 
as well as on account of the difficulty in finding an abundance of the 
early stages of development. 
The writer 1 ) has already given the following account of conjugation 
in Z. Moelleri using stained material. The figures given refer, however, 
to the present paper. “In the simpler case illustrated by the more 
common made of conjugation, a terminal portion of an erect hypha is 
distinguished by a septum from the portion below. Immediately beneath 
this septum is produced a branch which, growing upward, recurves to 
meet the side of the slender zygophoric filament cut off by the septum 
already mentioned (figs. 1, 9, 16). The two zygophores are from the 
beginning unlike in character as well as in origin. While the first, which 
contains but a small amount of protoplasm that becomes massed at the 
point of contact with the other, undergoes no further development, the 
second, which has arisen immediately below it, is from the outset richly 
supplied with dense protoplasm. Immediately after contact a progamete 
is developed as a perpendicular outgrowth from the slender erect zygo¬ 
phore, and in juxtaposition to this a progamete is formed by the terminal 
enlargement of the more vigorous zygophoric branch (figs. 2, 10, 17). 
In each of these progametes a transverse septum is formed, distinguishing 
the gametes which are unequal in size, the larger being formed on the 
side of the vegetatively more vigorous zygophore (figs. 4, 11, 21). This 
1) Sexual Reproduction in the Mucorineae (Proc. Amer. Acad. Arts and 
Sciences 1904, 40, 205—319). 
