108 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
looked upon as a natural and a necessary result of a new method 
of spore “cutting,” and that it could not have arisen in the zoospo¬ 
rangium. That the new method referred to occurs in the ascus 
has not been borne out by my observations and that epiplasm might 
not have arisen in a zoosporangium is at least debatable. Granted 
nuclear control in sporogenesis, and a tendency towards a reduc¬ 
tion in the number of spores without a corresponding and syn¬ 
chronous decrease in the protoplasm (a common feature in many 
Ascomycetes), and add to this, if need be, the acquirement of a 
precocious habit of spore-forming (especially if this means that the 
young spores depend to a large extent upon the contents of the 
spore sac, as is the case in asci) then epiplasm might very naturally 
be expected to follow in the zoosporangium, and without a change 
in the method of spore delimitation. 
On the whole it does not appear incompatible with the facts to 
suppose that the homology of a Saprolegniineous zoosporangium 
with an ascus is at least a possibility, if, of course, there is no onto 
genetical disqualification. As to that, if the Ascomycetes have 
sprung from the Oomycetes, then the regular alternation in the 
production of sexual and asexual organs exhibited by them has 
probably come about by the production, in certain transitional 
Oomycetes, of sexual organs only on the mycelia growing from the 
zoospores, their zoosporangia being suppressed or transformed into 
conidia, and the production of zoosporangia only by the mycelia 
growing from fertilized eggs. The latter zoosporangia have become 
asci. 
It should be stated here that Juel (: 02a) and Barker (: 03) have 
recently expressed the view that the ancestor of the ascus is an 
Oomycetous zoosporangium. They reach their results, however, by 
a method that should be used onlv with great caution. They ground 
their conclusion on an analogy between spore-forming in the ascus 
and the oogenesis of the Oomycetes. The raison d’etre of such an 
argument is based upon the theory that oogonia and antheridia are 
derivatives of algal gametangia, and that in the lower algae the 
gametangia are indistinguishable from and probably homologous 
with zoosporangia. 
For the last two suggestions concerning the origin of the ascus 
there is little more to be said on the basis of the phenomena of 
sporogenesis. If the ascus could have been developed from the 
