Pieters : Ferax Group of Saprolegnia 
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but each one was accompanied by an antheridium and the latter 
was either diclinous or androgynous. When such a mycelium 
was transferred to a solution in which the levulose was replaced 
by an equal concentration of dextrose, the oogonia produced were 
fewer, but very much larger and not more than 5 per cent, had 
antheridia. It is evident then that the number of antheridia 
present may vary with conditions, and that there may also be a 
natural variability independent of food conditions ; the place of 
origin of the antheridia is also variable. Shall we then go back 
to Pringsheim’s notion and consider these all forms of the same 
species? To one who has carried many pure cultures of these 
organisms through several years and who has observed how 
quite constant each form is under a certain set of conditions, this 
is out of the question ; the forms are different. It is evident that 
these species make up a group of closely related forms represent- 
ing tendencies to vary along different lines. Of these, S', monoica 
has the rnost complete sexuality with antheridia of prevailing 
androgynous origin ; S', mixta has less complete sexuality, antheri- 
dia of prevailing diclinous origin and a more delicate mycelium ; 
while S', ferax represents a complex of forms in which the loss 
of sexuality has gone much further that it has in the other species. 
The members of this last subgroup are probably very numerous. 
There is, of course, no doubt but that the form studied by de 
Bary was as he described it, almost free from antheridia. 
The form studied by Coker differed slightly from the ones I had, 
and Dr. Kauffman has verbally stated that the form he collected 
as S. ferax had many barrel shaped oogonia. Altogether, there 
seem to be almost as many forms as cultures studied, but all agree 
in the small number of oogonia found with antheridia. There is 
no intergradation between the forms with few antheridia and 
those clearly belonging to S. mixta, with one half or more of the 
oogonia accompanied by antheridia. Furthermore, so far as 
records go and so far as my own experience goes, the forms with 
a large number of antheridia have always had the “ slender” 
mycelium first described by de Bary. Until further work throws 
additional light on this matter I am inclined to believe that all the 
forms with stiff, strong mycelium and a small number of anther- 
idia on fly cultures at a temperature of 12 to 15 degrees C. must 
