OBSERVATIONS ON THE PROTOZOA 
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337 
and colorless, and established within an algal filament. Edmond- 
son reports having seen Vampy fella but once, and then only 
in a dark granular phase. His specimen assumed the inter- 
esting flagellated stage, which mine did not. 
Subclass AMOEBEA. 
*Hyalodiscus Umax (Duj.I 3 and 4, figure 53. 
Body oval or disc-shaped. Progression snail-like with a broad, 
clear anterior region and very little change occurring in out- 
line. Ectosarc relatively extensive. Nucleus visible without re- 
agents. Size 44 microns. 
So far as I have able to ascertain, this amoeba has not pre- 
viously been recorded in Iowa. Whether this indicates its rarity 
or a rather prevalent skepticism as to its being a distinct species 
I cannot say. I have never seen other amoebae so active as these 
are while they retained such regular outline. They were ob- 
tained in small numbers in December from under an inch of 
ice in an old stone quarry pond near the University. An in- 
teresting point was the presence of a minute, black, dancing 
organism in the contractile vacuole of one specimen (see figure) . 
*Difflugia species./ 5, figure 53. 
Shell hemispherical, proportions like Arcella but structure like 
Difflugia. An inverted rim within the mouth as is often seen 
in Arcella. Color white. Diameter 70 microns. 
Only one dead shell of this form was found. It does not 
correspond to any species described by the authors in my bib- 
liography. However, Difflugia is now believed to be extremely 
variable within its species, and this is probably nothing new. 
Arcella vulgaris Ehr. 6 and 7, figure 53. 
Observation of even , this most common of all rhizopods may 
occasionally be rewarded by a glimpse of something a little out 
of the ordinary. In October, in an old jar in the laboratory 
there suddenly appeared countless numbers of active, minute 
and colorless individuals. Figures 6 and 7 show a case of sup- 
posed conjugation of two of these young shells, a. smooth and a 
pitted variety . Since the two shells were not actually seen to 
approach each other and fuse there is of course a possibility 
that the process was division. Many writers record the union 
of two or more rhizopods, but remark upon the rarity of seeing 
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