372 Kauffman. — A Contribution to the 
together as the ( ferax 5 group. Maurizio also found that many species of 
Saprolegnia which he met produced no oogonia, but he only tested them 
with ordinary substrata. 
(H), (F), and (C) were kept vegetative for six months at a time by con- 
tinued cultivation on beef-gelatine. It was found best to transfer from the 
old to the fresh plate as soon as the mycelium had reached the margin of 
the dish, as it was noticed that when the culture was allowed to get too old 
the transferred hyphae no longer grew. This was either due to the accumu- 
lation of waste toxic substances produced by metabolism, or to famishing 
on account of the inability of the hyphae to get at the gelatine, the sub- 
stratum immediately surrounding them being rapidly dissolved by the 
proteolytic enzyme secreted by the fungus. In order to determine this 
point 'a culture of S. hypogyna was made in a flask containing 500 cc. of a 
5 per cent, maltose and a o-i per cent, peptone solution. The mycelium 
rapidly filled the liquid, forming a thick mat near the surface and remaining 
in a vegetative condition for thirteen months. The mass was then taken 
out, carefully examined, and a new culture made from it on beef-gelatine. 
After a time it was tested and found to produce the same reactions of 
S. hypogyna already recorded for that species. The mycelium from the 
thirteen-month culture was found to be in part disintegrated, in part filled 
with a very thin protoplasmic content somewhat granular in appearance, 
while a number of the end hyphae appeared normal. These apparently 
still retained the necessary vigour for further growth on a favourable sub- 
stratum. No reproductive hyphae could be found either in the loosely 
wefted peripheral zone of the mass nor in the interior. Vegetation there- 
fore took place for thirteen months without the renewal of the substratum 
and in spite of the chemical substances excreted during the metabolic ac- 
tivities of growth. This is possible because, as Klebs has shown, the meta- 
bolic products of a carbohydrate substratum are much less harmful than 
those of a proteid substratum. The latter is always found unfavourable for 
the continued existence of the fungus because of the toxic character of the 
waste products excreted. The small amount of peptone used supplied the 
necessary nitrogen, without interfering with the life of the fungus. 
The proposition of Klebs, now pretty well accepted, that the fungus can 
be kept indefinitely in a vegetative state, seems to be well founded. Klebs 
himself kept 5. mixta in a vegetative condition for six years, and all the 
species studied by me were kept at least six months without producing 
zoospores, oogonia, or gemmae of any kind ; and, as just seen, S. hypogyna, 
which can be made to reproduce most abundantly within a few hours or 
days, was kept from doing so for thirteen months ; at the end of that time 
it was able to produce oogonia in three days. 
Although it seemed superfluous to repeat all of Klebs s experiments, a 
set of cultures was prepared to study the effect of the different concentra- 
