407 



Ordinarily this species develops in swarms but it never occurred in 

 quantity in tlie pond. 

 Trachelomonas annata Etirenberg. 



Obtained Jan. 18 and Feb. 2 by the same method as Peridinium, already 

 described. 



Ciliata — 

 Halteris sp. 



Common among algse 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 ElirenTierg. V. campa- 

 nula Ehrenherg 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 // long and 

 from 20 to 30 /i 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- 



