405 
The data concerning elevation were taken in part from the United 
States relief map of the Bloomington quadrangle, and in part from aver- 
ages of the barometric readings. The bench mark established by the survey 
on the university campus rendered exact correlation possible. 
The following annoted list of species gives a fairly complete picture of 
the life in this pond. The list of flagellates and desmids is not exhaustive. 
The diatoms were not identified because of the inadequacy of accessible 
literature. However, it may be stated that the diatom flora consists of 
bottom inhabiting forms. 
Rhizopoda— PROTOZOA. 
Difflugia globulosa Dujardin. 
‘this was the most common protozoan in the pond. It was found at all 
seasons but was more common in 1910 than in 1909. It is reduced in 
nuinbers during the winter but when the temperature begins to rise in the 
spring, this species begins to increase in numbers. In 1910 this increase 
was very regular from March to August. The Difflugia in the quantitative 
plankton collections of that vear belonged for the most part to this species. 
In these collections the number per 100 liters varied from 28 on February 8 
to 39,780 on August 12. 
Diflugia oblonga Ehrenberg. 
This variable species was a common form in 1909 but not so plentiful 
in 1910. 
Diffugia acuminata Ehrenberg. 
Not common. 
Difflugia urceolata Carter. 
Common in the winter of 1909-10. Greatly outnumbered by D. globu- 
losa in the spring and summer. In plankton material killed in formalin, 
I found a typical individual of wrceolata with the mouth of its shell closely 
appressed to that of a specimen of D. Globulosa. Whether this was a case 
of fission, an animal building a new shell or an accident, I am unable to 
state. I am inclined to the belief that the animal was dividing. The 
rounded shell was slightly smaller than the spined one. If this be true, 
the distinction between the two forms is of course not specific. 
Difflugia corona Wallick. 
Observed occasionally. 
Difflugia lobastoma Leidy. 
Rare. 
