PROTOZOAN FAUNA OF HAY INFUSIONS 209 
in these it has been quite striking, and in one of the later infusions 
I was able to predict correctly that declining amoebo-flagellates 
would be replaced by typical amoebae. Such a cycle, of course, 
would not be remarkable in view of the results of some investi- 
gations on amoebae.“ Although the data from these infusions 
by no means prove that the forms represented in this cycle are 
stages in the life history of a single species, nevertheless I lean 
toward the view that such will prove to be the case (ef. p. 211). 
Taken as a whole, the study of the bottom fauna has proved to 
be less interesting than was anticipated, as I had expected to find 
Fig. 12 Comparison of the Paramaecia fauna at the bottom of infusion Bi 
( ) and infusion B2 (- - -). x = point at which an epidemic of conjugation 
occurred in B1. 
a much closer correlation between declines at the top and rises 
at the bottom, and vice versa. Apparently the bottom forms are 
largely independent of those at the surface, and the protozoan 
types under consideration, with the exception of the amoebae, are 
represented at the bottom by considerable numbers of active indi- 
viduals chiefly when some sudden change, such as the falling of the 
zoogloea, brings them down, or by stragglers which manage to 
exist by avoiding the competition at the top. It is nearly always 
possible, by careful searching, to find at the bottom a few strug- 
gling individuals which have survived from an earlier prosperous 
surface population. 
14 For example, cf. Metcalf: Studies upon Amoeba. Jour. Exp. Zool., vol. 9, 
1910. 
