CERTAIN SPECIES OF Mucor 243 
detail. They used soil extract with 10 per cent. gelatin or 1.5 
per cent. agar, but inasmuch as some fungi grew very slowly on 
these media, they added 2 per cent. of either saccharose or glucose. 
The following nutrient also proved very good in some cases: ‘“‘ wort 
55, water 50,”’ saccharose 2 per cent., gelatin 10 per cent., or agar 
1.5 percent. This medium always gave an acid reaction, but was 
used without neutralization. The manipulation may be outlined 
as follows: a fragment of humus from near the surface of the soil 
was introduced into a (previously sterilized) ‘platinum crucible. 
About I c.c. of sterile water was then added, and the fragment 
of humus was triturated with a flamed glass rod, flattened at the 
end. A small amount of this infusion was transferred with a 
platinum loop to a test tube containing about 10 c.c. of water. 
The contents of the test tube were then emptied on a poured plate 
(Petri dish), which was inclined so as to allow the excess water 
to drain off. Their so-called pure cultures were made in one 
of the following ways: by cutting out a piece of the substratum 
with the organism on it; by transferring a fragment of the my- 
celium; or by transferring some spores to a newly poured plate. 
In Hagem’s (1908) method we are at once impressed with the 
fact that to him pure cultures from a single spore are prerequisites 
for any investigation. His method is as follows: with a platinum 
needle some spore material was transferred to a flask containing 
about 30 c.c. of sterile water. After a vigorous shaking to separate 
the spores, a few cubic centimeters of the dilution were poured 
into a second flask containing water. This was repeated once 
more and then 2 c.c. of this final dilution were poured into a 
Petri dish containing solid nutrient material, care being taken 
that the entire surface was moistened; the excess water was 
then poured off. After the cultures had stood for two or three 
days at room temperature, the cover of the Petri dish was re- 
moved and the plate was examined under the microscope for 
an isolated growth derived from a single spore. If such was found, 
it was cut out and transferred with a small amount of the sub- 
stratum to a new dish. In his isolation of the soil-inhabiting 
forms, Hagem simply sprinkled a small amount of soil over three 
or four Petri dishes containing nutrient media. The one caution 
that he gives is that forms must be separated as soon as the 
