PROTOZOAN FAUNA OF HAY INFUSIONS 229 
of the infusion’s life. The growth of Colpoda in this group of 
infusions is remarkable for its abundance and persistence, for 
during the greater part of the life of the infusion, Colpoda was 
the form which dominated. 
A IV group. Colpoda was the second form to attain its max- 
imum, which occurred on the 13th day with 2500 per ce. present. 
This number persisted to the 17th day, and then a very quick 
decline ended in the extinction of the form four days later. 
BIgroup. Colpoda was the third to attain its maximum, being 
preceded by the monads and the hypotrichida. Its maximum 
occurred on the 14th day and this was followed by a slow decline 
resulting in the disappearance of Colpoda on the 30th day. 
BII group. Colpoda attained its maximum abundance on the 
6th day, then rapidly proceeded to its extinetionon the 15th day. 
The notably small development of Colpoda in this group of in- 
fusions is paralleled by that of all the other organisms in B /T. 
BIII group. In this group of infusions Colpoda rose rapidly 
to a maximum of 8000 per cc. on the 18th day, and then fell even 
more rapidly to extinction on the 29th day. In this series of 
infusions Colpoda was again the dominant form, greatly outnum- 
bering the hypotrichida and paramaecia whose small maxima 
occurred before its own. 
BIV group. The appearance of Colpoda occurred relatively 
late, none being observed until the 6th day, and its maximum 
growth occurred on the 12th day, and its extinction on the 16th 
day. In this series it was the fourth form in point of time to 
reach its greatest abundance. 
CI group. In these three cultures the average maximum num- 
ber of Colpoda, 4500 per ec., occurred on the 15th day, after a 
rapid rise from the 7th day. Then there was an equally sudden 
decline to about 40 per cc. by the 22nd day, and this number 
gradually decreased until it became negligible at the 46th day. 
C III group. Again in this culture the growth of Colpoda 
over-shadowed that of all the other forms. Appearing on the 4th 
day it gradually increased until a maximum of about 15000 per 
cc. was attained on the 33rd day. This was sustained for four 
days and then a remarkable decrease brought it down to about 
THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 12, NO. 2 
