10b PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
unlike, and the following differences have been insisted upon by 
certain botanists as being incompatible with any view that homol- 
ogizes ascus and sporangium: (1) that in the sporangium the nuclei 
are perhaps not at all functional in the delimitation of the spores, 
while in the ascus they are the direct agents; (2) that the process 
of spore delimitation in the first case is an act of cleavage (previ¬ 
ously or not at all marked out by hyaline areas), while in the latter 
it is a literal cutting out of the spore plasm by a plasmatic mem¬ 
brane; (3) that the plasma membranes of the sporangiospores are 
extensions of previously existing plasma membranes, while those of 
the ascospores are composed of fused astral rays; and (4) that 
there is an epiplasm in the ascus, but none in the sporangium, and 
that this is because of two fundamentally unlike methods of spore 
delimitation. 
There is, I am inclined to think, some question as to the validity 
of the first of these contentions in regard to the sporangium. Thus, 
as far as Saprolegnia is concerned, nuclear control in spore forma¬ 
tion seems almost a certainty, for the spores that are formed are 
constantly uninucleated and never enucleated, and the nuclei are 
practically the centers of the cleavage areas. And even in the 
Zygomycetes it is difficult to conceive of control being entirely 
transferred to the cytoplasm, for, in the forms that have been inves¬ 
tigated, it is notable that nuclei are never absent from the proto¬ 
plasmic masses resulting from the cleavages. Incidentally it may 
be observed that if spore formation in the Zygomycetes is due to 
the activity of the cytoplasm, but in the Oomycetes to the activity 
of the nuclei, then it would appear that the value of the cytology 
of spore formation as a factor in deciding phylogenetic problems 
between fairly widely separated groups is rather questionable. 
Nuclear control in the Ascomycetes is undoubted. Indeed, cer¬ 
tain phenomena demand comment. Thus even the shape of the 
nuclei changes throughout the process, a feature that seems unique. 
Timberlake (: 02 ), however, has observed somewhat similarly shaped 
nuclei in some cases in Hydrodictyon, and his observation was that 
the pointed end lay near the newly formed plasma membranes and 
that the occurrence was only noted when cleavage followed closely 
on nuclear division. In explaining this phenomenon it must be 
borne in mind that spore-forming in the Ascomycetes is precocious, 
that the spores are being delimited and the spore plasma differenti- 
