410 
of these worms are always filled with decaying vegetable matter. They are 
ravenously eaten by Amblystoma larvie and Diemyctylus. These two facts 
probably account for their occurrence in this limited habitat. 
CRUSTACEA. 
Arthropoda— 
Daphnia pulex DeGeer. 
Occurred twice, in March and April, 1909, and in May, June and July, 
1910. Its maximum occurrence was on June 15, 1910, when there were 80 
per hundred liters of water. In towing collections, often but a single 
specimen was taken. 
Simocephalus vetellus Mueller. 
The most conspicuous crustacean of the pond. It is numerous at all 
seasons among the plants and plant remains. It is rarely taken in the 
cpen water of the central part of the pond. Adults were taken two days 
ufter the rain which terminated the drouth in 1908. It was found that in 
cultures it takes from 10 to 12 days for adults to develop. From these 
facts, it appears that this crustacean was able to survive the drouth as an 
adult. To do this, it must have worked its way down through the vege- 
table debris to the water level. It is present at all periods of the year, 
producing a maximum of 25 young in a brood. It makes a slight diurnal 
vertical migration. This is difficult to demonstrate quantitatively because 
of its habitat. If the surface of the water be “skimmed” with a fine 
meshed net during the day, very few if any individuals are taken. How- 
ever, many individuals are taken by this operation at any hour of the 
night during the summer months. 
Alona quadrangularis Miiller. 
Appeared in March, 1910. Taken with young in brood chambers. 
Never more than 120 per hundred liters until May 28, when 696 per hun- 
dred were taken. It varied during June, July and August from 500 to 780 
per hundred liters, the maximum occurring on Aug. 12. Eggs were present 
in brood chambers in a large per cent. of them from April till August of 
this year. 
Cypridopsis vidua Brady. 
Appeared as soon as the pond began to fill with water in Noy., 1908. 
During the following winter and spring it was one of the most conspicuous 
forms. No attempt was made to estimate its numbers, but a small quan- 
