463 
Zygospores of Sporodinia grandis. 
protoplasm. The masses retain their individuality for a short time after the 
resorption of the wall, and the region of contact reacts somewhat differently 
to the stains (PL XXXV, Fig. 6). Ultimately, however, the line of fusion is 
obliterated, and it is impossible to distinguish any difference between the 
two masses of protoplasm. Gradually, as the mixing of the protoplasm 
progresses, it passes from a dense homogeneous nature to a vacuolar 
condition. It is at this stage that occur what appear to be nuclear fusions. 
They are first evident along the line of contact of the two protoplasmic 
masses, and later throughout the whole structure as it becomes vacuolated. 
In fusion, the nuclei present the usual appearance of fusing nuclei. They 
come to lie in pairs, the nuclear membrane disappears between them, and 
the deeper staining central masses previously described come to lie within 
a single membrane. Ultimately, these two masses fuse, and one larger nucleus 
results containing a single deeply staining central portion (PL XXXV, 
Fig. 7 a). 
The question at once arises as to whether this condition just described 
might not be a process of division of the nuclei instead of fusion. The 
process might be viewed from either standpoint, and it is probable that 
the divisions described by many of the previous workers on this problem 
have been so interpreted. As has been said, the nuclei are so small that 
even under the highest magnification available, approximately 2,000 times, 
it is impossible to be absolutely certain on this point. There are, however, 
several resultant conditions that have seemed to justify the present inter* 
pretation. In the mycelium, in the germ-tube of the germinating spore, 
in the sporangia, and in the gametangia before resorption of the separating 
wall, the nuclei are small and not well defined (PL XXXV, Figs. 1, 2, 7 a ). 
In later stages, however, the nuclei are larger, and the nuclear membrane 
is more distinct. 
The fusion of the nuclei results in the presence of nuclei of two sizes in 
the young zygospore. The protoplasm assumes a thready nature, and 
throughout the whole zygospore there is evidence of a nuclear disorganiza- 
tion (PL XXXV, Fig. 8). This appears to be restricted to the smaller 
nuclei. A characteristic zonation occurs'about this time. The majority of 
the nuclei that are undergoing disintegration appear to be concentrated in 
a zone around the periphery, while those towards the centre retain their 
normal form. When the nuclei begin to disorganize, the outer membrane 
remains distinct for some time, but the inner portion loses its granular 
appearance. The central red-staining mass increases in size as if being 
dissolved, and stains less densely. The whole nucleus appears eventually 
as a large red-staining mass (PL XXXVI, Fig. nr). The nuclei of the 
suspensors present a similar appearance as they degenerate, following the 
delimitation of the gametangium. 
About this time, there appear numerous spherical bodies of cytoplasmic 
