D. L. Mackinnon 
179 
There is great variability in size. The average dimensions of the 
entamoeba of Type 1 are 8 /j, x 5 fi with a nuclear diameter of 3 /u.. 
Individuals are met measuring as much as 16 /a x 15 /x, while others are 
as small as 5 fx x 5 /x. Type 2 is usually rather larger than Type 1. 
16 /u, X 17 /i is a common size, with nuclear diameter of 4 /x. Some are 
as large as 25 fx x 22 /x: others as small as 8 fx x 5 /x, or even less. 
The details of division and encystment have not been worked out, 
and it is therefore not possible to tell yet whether there are here two 
different amoebae, or only two aspects of the same species. With more 
material at my disposal, I hope soon to settle this point, 
II. Flagellata. 
I find no less than six different flagellates in Tvpula, viz. a Tricho- 
mastix, a Monocercomonas, a Polymastix, a Hexamitus, and two species 
of Embadomonas. 
1. Trichomastix. This flagellate resembles in all important respects 
the trichomastix described by me from the larvae of Trichoptera. In 
all the stages that I have found hitherto—the ordinary flagellate 
individuals (8 /r, x 4 p), dividing forms, and multiplication (?) cysts 
Fig. 9. Cyst of Trichomastix from Tipula. 
(5 /i X 4 fx) (Figs. 6, 7, 8 and 9)—this flagellate, except for its rather 
smaller size, is morphologically indistinguishable from T. trichopteroruvi 
Mackinnon. In the dividing flagellates and in the cysts, the chromatin 
shows a marked tendency to group itself into four masses (chromosomes ?) 
at each pole. 
It occurs in about 30 ‘’/o of the infected larvae. 
2. Monocercomonas. This is a pear-shaped or spherical organism 
without definite periplast (Figs. 10 and 11). Its dimensions vary from 
6/u.x3yato9/r-x5^. The four flagella, which appear to be of approxi¬ 
mately equal length, are disposed in two groups of two at the anterior 
end of the body, the groups usually being separated from one another 
by a distinct space. The nucleus, which lies at the anterior end of the 
organism, is of the “vesicular” type, with a well-marked caryosome, 
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