380 
Kauffman . — -A Contribution to the 
Klebs found that different species of Oedogonium behaved very differently to 
a change from light to darkness in the effect this change had on the pro- 
duction of zoospores. I have been able to verify this for several species of 
Oedogonium in our laboratory. It is therefore not surprising to find similar 
differences of a deep-seated nature present in the various species of Sapro - 
legnia. We need further experiments with these forms in order to determine 
the conditions. 
The two forms of Saprolegnia which I have denominated (H) and (F) 
need further discussion. In all the essential characters except the number 
of antheridia these two forms would come under Saprolegnia mixta. 
(H) comes more nearly to it except that about 70 per cent, oogonia have 
normally antheridia, and this can be increased to over 90 per cent. This 
form approaches S. monoica in its many antheridia, and it is very probable 
that under the most advantageous conditions all the oogonia would bear 
antheridia. But 6*. monoica has been described as having only androgynous 
antheridia, larger than those of 5 . mixta , and with long and stout vegetative 
hyphae. On the basis of what we have learned concerning the variation of 
antheridial filaments of .S'. hypogyna , it would seem that the androgynous 
origin of antheridia was not likely to be constant enough to warrant keep- 
ing two species separate on its account. It seems to me, however, that this 
is too large a conclusion. For, although no genuine S. monoica was found 
in my cultures, it seems likely from Humphrey’s careful observations that 
the size of the hyphae and antheridia, as well as the usually ‘ indescribable 
differences ’, make this an easily recognizable species ; Humphrey also 
points out that it is comparatively rare. I can, therefore, not subscribe 
to the suggestion made by Davis (’ 04 ) that .S'. mixta is only a cultural form 
of .S', monoica or vice versa. But neither does my plant (H) seem to be 
exactly the form described by De Bary, since both he and Klebs found that 
50 per cent, was the highest number of oogonia which were supplied with 
antheridia. 
This would hardly be a point on which to insist, if the results from my 
study of (F) did not also warrant it. The cultures of (H) and (F) were 
made side by side, and constitute checks on each other with reference 
to temperature, &c., so that the uniform differences must be considered con- 
stant. Each was derived from a single zoospore, and the cultures were kept 
from becoming contaminated. When the cultures were made on wasps, 
(F) had from 1 to 2 per cent, antheridial oogonia, while those of (H) 
amounted to 75 per cent, or more; in leucin solutions those of (F) gave a 
maximum of 25 per cent., while those of (H) yielded as high as 95 per cent, 
of antheridial-bearing oogonia. It seems to me that we must consider these 
as separate entities which are closely related to the Saprolegnia mixta of 
De Bary, and that they will remain distinct along with that species when all 
are placed under the same conditions of culture. Nor does it seem to me 
