220 LORANDE LOSS WOODRUFF 
dition of, for example, the A J cultures at the end of the first fifteen 
days, with the A JI/J cultures at the end of the same length of 
time without taking the temperature into account. However, 
it is fair to compare the relative time of appearance of the various 
organisms in A J and the relative time of appearance of the var- 
ious organisms in A ///; but even here an error is undoubtedly 
present, though, it is believed, it is not sufficiently marked to 
appreciably influence the general results though minor variations 
which occurred in particular infusions may well be due to it. 
This error arises from the fact that the different species of organ- 
isms in the infusions undoubtedly have their own optimum tem- 
perature for development and consequently it may be supposed. 
that a particular form, which has a comparatively high optimum 
temperature, may reach its maximum later than another with 
a slightly lower optimum temperature, in the cultures existing 
during the early part of April when the general average tem- 
perature was lower, while it may attain its maximum earlier than 
the latter in the cultures which reached a corresponding stage of 
their development when the temperature was generally higher. 
As already stated, the first intention was to follow the entire 
fauna and flora which developed in the infusions, but this involved 
more labor than could be performed accurately by one observer. 
Consequently although a record was kept of all the animals and 
plants which actually were observed, these data will not be pre- 
sented because I am not satisfied that they are sufficiently accur- 
ate or comprehensive. One who has not attempted to follow in 
detail a series of cultures, started in the manner described, has 
not, I think, an adequate realization of the wealth of forms which 
will develop. Some of the forms appear and disappear with such 
marvellous rapidity that if they are not immediately identified, 
in many cases it is impossible to do it later. Therefore, I repeat 
that the description which follows simply affords the data col- 
lected in regard to certain well-known genera and groups of Pro- 
tozoa, which appeared in sufficient numbers, in a large majority 
of the infusions, to render their study of value in attempting to 
reach some general conclusions as to their sequence in such in- 
fusions under the conditions of the experiment. It is believed 
that the concentration of attention on these few forms is prefer- 
