ATKINSON: THE GENUS ENDOGONE ff 
homogeneous as in the gametangia. But as the new zygote enlarges 
the cytoplasm becomes coarsely reticulate. The strands are coarse 
and with an irregular outline. They radiate irregularly from the 
center to the periphery and anastomose by irregular branches, forming 
a large meshed network the strands of which are coarser in the central 
region, thinner toward the periphery. During the early stages of 
development of the young zygote the nuclei appear to have a general 
distribution, but have not been observed near the periphery. As the 
zygote approaches its full size the nuclei occupy the more central 
region, being distributed from the center to a zone half way, or a 
little more, to the periphery.. Sometimes the centralization is more 
marked. At this stage there appears to be a differentiation of the 
cytoplasm, or rather, the appearance of a clear homogeneous plasma 
occupying the nuclear region and in which the nuclei die. When the 
nuclei are strongly centralized, the homogeneous plasma appears to 
form a single large central area. When they are more widely dis- 
tributed, the homogeneous plasma is separated into several areas, 
each area containing several nuclei. During all this period the coarsely 
reticulate cytoplasm occupies the entire zygote. 
A provisional suggestion as to the function of this homogeneous 
plasma is that it serves as a medium for the freer movement of the 
nuclei than can take place in the coarsely reticulated cytoplasm; or 
the homogeneous plasma may actually serve to move the nuclei to a 
certain extent, possibly bringing them into closer proximity in the 
center and later carrying them into the peripheral zone. In this 
central region the nuclei are generally in pairs and the two nuclei of a 
pair appear to fuse. This fusion of paired nuclei in the zygote corre- 
sponds with the fusion of paired nuclei in certain of the Mucorales as 
described by Gruber (1901) in Sporodinia grandis, Dangeard (1906) in 
Rhizopus nigricans, and Moreau (1911-1913) in Rhizopus nigricans 
and species of Zygorhyncus. The fusion of the nuclei of a pair is 
suggested by the fact that they are found close together, sometimes 
the nuclear membranes in contact, again an elongated nucleus (? 
fusion) with one membrane and this constricted between the two 
nucleoli, and further two nucleoli surrounded by one membrane which 
is not constricted. Of course these relations might be the result of 
nuclear division, but no figures appear at this stage which suggest a 
division of the nuclei. 
In a later stage of development the coarse reticulum of the cyto- 
plasm disappears. The cytoplasm becomes more homogeneous. 
The nuclei appear to occupy a zone about half way between the 
center and periphery. Figures are present which suggest a division 
of the nuclei at this stage, for the nuclei are often two to three times 
