Sf 
waters, and of these parasitic forms will reveal the great richness of 
the ciliate fauna in this aquatic environment. 
SUCTORIA. 
Average number, 332. This class is not quantitatively 1m- 
portant in the plankton, being represented,in so far as our records 
go,only by adventitious or passive planktonts. No limnetic species 
has as yet been found in the Illinois. An examination of the 
littoral region during the prevalence of ciliates will probably yield 
a rich suctorian fauna. 
DISCUSSION OF SPECIES OF SUCTORIA. 
Acineta linguijera Clap. and Lach.—This species is usually found 
on aquatic Coleoptera. A single occurrence of an unattached indi- 
vidual was recorded June 21, 1898. 
Metacineta mystacina Ehrbg.—Average number, 301. This 
species occurred in the plankton from March till October in 1898 and 
in the winter months of 1899, at irregular intervals and in small 
numbers (Table I.). Most of its occurrences attend flood invasions, 
and it is evidently adventitious. It is frequently attached in the 
plankton to minute particles of debris. This species varies greatly 
in the size of the lorica. Sand (’01) gives the range in height as 
from 33-700. The variation in proportions has given rise to a 
number of descriptions of new species by Stokes (’88 and ’94) and 
Maskell (’87), but an examination of a series of individuals such as 
appear in the plankton shows that they intergrade so closely that 
specific distinctions can not be maintained for the variants. Meta- 
cineta appears throughout the whole range of temperatures, no 
seasonal predominance appearing in the records. 
Podophrya fixa O. F. Mill—Average number, 12. This species 
is also adventitious in the plankton. It was recorded in March and 
September at 37° and 73°. Cysts were noted January 21. 
Tokophrya quadripartita Clap. and Lach.—Average number, 4. 
Adventitious in the plankton in March and November. Hempel 
(99) finds it most abundant in May and June, associated with 
Epistylis plicatilis and Opercularia irritabilis on crayfish, insect 
larvee, and turtles. 3 
Tokophrya cyclopum Clap. and Lach.—Found occasionally upon 
Cyclops during spring and summer. 
(10) 
