407 
Ordinarily this species develops in swarms but it never occurred in 
quantity in the pond. 
Trachelomonas annata Ehrenberg. 
Obtained Jan. 18 and Feb. 2 by the same method as Peridinium, already 
described. 
Ciliata— 
Halteris sp. 
Common among alge at south end of pond, Apr., 1910. 
Vorticella. 
This genus occurred sporadically during the warmer months. Specific 
identification was not made every time it was observed. 
It was present as late as Nov. 25, 1909, and reappeared in May. The 
most common form was referred to V. microstomata Ehrenberg. V. campa- 
nula Ehrenberg was present in large quantities Oct. 26, 1910, when the 
water temperature was 13.6° C. 
Epistylus sp. 
A ciliate belonging to this well marked genus was taken March 11, 
attached to the edge of the thorax (usually near the posterior angle) of an 
aquatic beetle. It is not referable to any species to whose description I 
have access. The zooids, when completely expanded, are 1/5 mm. long by 
1/12 mm. wide. The stems branch dichotomously and are segmented at the 
base of each branch. The planes of successive branchings are usually at 
right angles to each other. The branches are from 30 to 40 yw long and 
from 20 to 30 » wide. From this method of branching the colony tends 
to form a spherical sector of increasing size. The outer surface of this 
sphere is formed by the zooids, which when contracted in a well developed 
colony, touch each other forming a continuous surface. The cell walls are 
fairly firm and a limited surface is exposed. Some water is probably re- 
tained among the stalks below the zooids. This seems to enable them to 
prevent desiccation in a degree. The following observations support this 
inference: A well developed colony attached to a bit of the thorax of a 
beetle was left on a slide under a cover glass at 4:20 p. m., room tem- 
perature about 70°. The water under the cover soon evaporated. At 7:50 
a. m. the following day, the slide was examined. The outlines of the con- 
tracted zooids were still discernible. The colony was removed to tap water 
in a stentor dish. At noon, about 20% had revived and were actively feed- 
