38 
Amoeba Chironomi, Nov. Sp. 
are faintly reddish in hue. A nucleus is present in the endoplasm. 
Food vacuoles were very rarely seen. 
Contractile Vacuole. The occurrence of a contractile vacuole is 
most unusual in parasitic Amoebae , but one is found in A. chironomi. 
The contractile vacuole (Figs. 1, 5, c.v .) or excretory organella has 
more resemblance to that structure as seen in Paramoecium than to 
that of the common Amoeba. There would seem to be a series of fine 
curved radiating slits or canaliculi having a superficial resemblance to 
portions of the iris diaphragm of a camera or microscope (Figs. 5, 8, 13, 
15, 16). The canaliculi are so thread-like that the vacuole never 
appears stellate. The vacuole at one time is widely expanded and 
ringlike (Figs. 4, 6, 7, 10, 12). It gradually contracts, the lumen 
remaining circular (Figs. 2, 5), and finally is obliterated (Fig. 11). It 
then re-opens. When widely expanded the contents of the vacuole 
appear faintly reddish. 
If the Aiyioeba be “fed” with methylene blue solution, part of this 
dye finds its way into the vacuole, whose purplish colouration then 
suggests that of polychrome methylene blue. 
Nucleus. In life, the nucleus (Fig. 1, n .) is seen as a clear vesicle, 
but it is not particularly obvious in all specimens, being obscured by 
the very granular endoplasm. I had very little material for making 
stained preparations, but in the few I have, the nucleus is simple, is 
more or less oval in form, and shows a small, denser staining portion, 
the nucleolus (Figs. 16, 17) often to one side. There is little chromatin 
in the nucleus, but the nuclear membrane is sharply defined (Figs. 
6, 16, 17). I regret that I have not definitely seen binary fission 
in Amoeba chironomi , and so have not found karyokinetic or other 
division figures in connection with the nucleus. This is probably due 
to the small amount of material at my disposal and to the season of 
the year (winter) when the work was done. One can hardly expect to 
find active multiplication of free forms in winter. Such division may 
occur at warmer periods of the year, or perhaps in older larvae of 
Chironomus than those examined. 
Encystment. 
Encystment of Amoeba chironomi can be induced in the laboratory 
by the simple method of allowing a preparation in physiological salt solu¬ 
tion to become concentrated by slight evaporation. Under the influence 
of heat and increasing salinity, the protoplasm is unable to continue its 
