Certain Protozoa and Other Invertebrates. Zot 
1. Avrcella vulgaris Ehrenberg 
Upon examining the stomachs of a number of tadpoles caught at the 
edge of Aubeenaubee Bay in August (1906), a goodly number of Avrcella 
vulgaris were obtained. The tadpoles when caught were busy sucking 
the surface of weeds and sticks, as is their habit, and from these they 
probably obtained the Protozoa. It is probable that Protozoa form an 
important part of the food of young tadpoles. On other occasions we 
have seen them taking in large numbers of Paramececium. 
Arcella vulgaris was abundant September 3 (1906), with other mate- 
rial (Paramecium) forming a scum over water in a tumbler where 
some duckweeds were kept. It was also present in hand-gathered mate- 
rial obtained at the dam in the Outlet, October 30, of the same year. 
2. Centropyxis aculeata Stein 
Taken occasionally in the summer and autumn of 1906 in gatherings 
in shallow water near shore. 
3. Euglypha alveolata Dujardin 
Obtained in collections near shore, summer and autumn of 1906. 
4. Dinobryon sp. 
Found occasionally near shore in Lost Lake, but not abundant. In 
the small lakes about St. Paul, Minn., where it is very abundant, it 
furnishes an important item in the food of the fresh-water mussels. 
5. Huglena viridis Ehrenberg’ 
Some found in a scum in pools in Green’s marsh. The great amount 
of vegetation makes the water almost as rich as an infusion. Obtained 
August 22 (1906). Euglena formed a bright green scum over the small 
pools. 
6. Volvow aureus Ehrenberg 
Not found by us at all in the lake, but exceedingly abundant in 
Farrar’s Pond and a pond east of the lake, in the spring of 1901, large 
swarms being seen there, a single dip of a common dipper always con- 
taining several examples. A large number of examples obtained from 
a small pond near the lake April 24 (1901). Its favorite habitat is in 
shallow pools, easily warmed throughout and containing in the bottom 
an abundance of dead leaves or similar fertilizing matter. This species 
was exceedingly abundant in the shallow, well-fertilized carp ponds at 
Washington, D.C., in the spring of 1906. 
7. Peridinium tabulatum (Ehrenberg) 
Taken rather less frequently in the vertical hauls than its relative, 
Ceratium macroceras, and apparently not very common. One might 
naturally expect it to be more common near shore. It was not noted 
often in surface hauls. It is a species of world-wide distribution, and 
probably is abundant where conditions are favorable. 
There is very little difference between the genera Ceratium and 
