222 LORANDE LOSS WOODRUFF 
aurelia and caudatum, indiscriminately. It is apparent, then, 
that no attempt has been made to identify the various species, 
as this would necessitate a large amount of labor entirely incom- 
mensurate with the value of the information gained for the prob- 
lem in hand. All of the forms included together are adapted to 
the same general environment (as the results which follow show), 
and therefore it is logical to consider them together as a’ unit with- 
out regard to the taxonomic variations of the individual moieties 
of which it is composed. 
B. GENERAL OBSERVATIONS ON THE COURSE OF DEVELOPMENT 
OF HAY INFUSIONS 
In infusions (A) made with boiled hay, which is allowed to 
remain in the jar, most of the hay sinks quickly to the bottom 
and remains there. In the cultures (C) made with unboiled hay 
most of the material floats near the surface for four or five days 
and then begins to sink gradually to the bottom. It is usually 
all at the bottom within two weeks. When the hay is allowed to 
remain in the infusion (A, C) this slowly disintegrates and is 
reduced to a more or less amorphous mass by the end of the sec- 
ond month. The rapidity of these changes, however, varies con- 
siderably with the temperature to which the cultures are subjected. 
When hay and water are combined the liquid rapidly becomes 
straw colored, and within the first few days bubbles of gas appear 
entangled amongst the hay at the bottom, and these rise by 
degrees to the surface. At comparatively high initial tempera- 
tures the gas will frequently disturb the hay and sometimes raise 
it to the surface. Peters’ observations show that this gas is 
chiefly CO,. By the third or fourth day the color of the culture 
liquid appears darker and this becomes increasingly pronounced 
until finally the liquid is of a dark brownish color. One familiar 
with infusions can, of course, readily tell the approximate age of 
a culture by its color. Fine’s studies on these infusions show that 
the light and yellowish shades of color are due to relatively high 
acidity; the darker and brownish shades to relatively low acidity.!° 
10 Fine. Loe. cit. 
