646 THE AMERICAN NATURALIST. [Vor. XXXV. 
observed will disappear within a few days, the tap water 
apparently not agreeing with them. Examination of the mate- 
rial from time to time during the ensuing month, however, 
shows the gradual return of the original organisms, and with 
this return the animals are much more numerous than before, 
and with the advantage that only one type of organism appears 
to occupy the stage at a time. Amada proteus comes along 
from four to six weeks after collection, and so constant is 
this appearance that I can plan in September for my classes 
in November. 
The addition of new tap water has a retarding effect upon 
the cultures, and a too rapid culture can be checked by this 
means. A slow culture, on the other hand, should be kept 
from evaporating and should not be replenished. 
In the present contribution I wish to offer a few notes in 
regard to some forms of particular interest that have appeared 
during the year, — forms which, for the most part, are rarely 
observed and but littleknown. Among theseare Nuclearia, Mas- 
tigamoeba, Multicilia, Lacrymaria, and a species of Actinobolus. 
It may be of interest, however, to enumerate some of the other 
forms that are found every year in this water. Of the Rhizo- 
poda there are four species of Amceba (not counting A. radiosa, 
the young form of A. proteus); two species of Pelomyxa, three 
of Difflugia, one of Centropyxis, Arcella, and Euglypha ; and 
of the Heliozoa, Actinophrys, Actinospherium, Acanthocystis, 
Pinacocystis, and the dainty stalked Clathrulina are frequently 
found. Of the Mastigophora there are several species of 
Euglena, Phacus, Astasia, Trachelomonas, Peranema, Chilo- 
monas, Cryptomonas, Petalomonas ; the beautiful colony form 
Poteriodendron, and the more common colonies Volvox, Pan- 
dorina, Eudorina, Gonium,andSynura. The minute choanoflagel- 
lates Monosiga and Codosiga, and the dinoflagellates Peridinium 
and Glenodinium, with their actively vibrating transverse fla- 
gella, occur in greater or less abundance. The more common 
forms of Ciliata in the pond are : Paramoecium, Dileptus, Bur- 
saria, Stentor, Spirostomum, Enchelys, Chilodon, Prorodon, 
Coleps, Urocentrum, Loxophyllum, Loxodes, Colpoda, Coeno- 
morpha, Gastrostyla, Urostyla, Euplotes, Kerona, Trichodina 
