236 LORANDE LOSS WOODRUFF 
rose to a maximum of about 500 per ce. on the 37th to the 42nd day 
after which there was a general decline to 200 per cc. at the last 
observation on the 64th day. 
C IV group. This organism appeared on the 31st day, at- 
tained its greatest abundance on the 44th day, with about 600 
per cc. present, and then declined to 200 per cc. on the 65th day, 
when the final examination was made. 
The results given above, when compared with those of the hypo- 
trichida, show that Paramaecium usually attains its maximum 
numbers at the surface when the hypotrichous ciliates have passed 
their period of greatest abundance. 
5. Vorticella 
Algroup. Vorticella made its appearance on the 30th day and 
increased gradually in numbers until the 65th day when about 
100 per ec. were seen. Then it rose rapidly to a maximum of 
700 per ce. on the 73rd day, declined equally rapidly to 200 per 
ec. by the 79th day, and then rose again to nearly 700 per cc. on 
the 86th day when the last observation was made. 
A II group. This form appeared on the 5th day and persisted 
in small numbers to the 27th day. From this point it rose to 3000 
per cc. on the 44th to the 49th day, and then quite rapidly de- 
clined to about 80 per cc. on the 67th day. Another rise to about 
500 per ce. occurred on the 75th day when the culture was dis- 
continued. 
ATIII group. Vorticella appeared on the 8th day and continued 
in almost negligible numbers until the 25th day when it began to 
multiply rapidly until the maximum of 700 per ce. occurred on the 
29th day. It then decreased to less than 20 per cc. by the 33rd 
day and remained in about this number to the 50th day, after 
which it again increased to 600 per ec. on the 57th day and declined 
to about 120 per cc. on the 64th day, when the last count was 
taken. 
A IV group. This form made its appearance on the 7th day 
and persisted in comparatively small numbers until the 26th day, 
