458 MR. H. SANDON ON PKOTOZOA FROBI THE 
APPENDIX. 
Notes on the Species found. 
1. Plagellata. 
Cercomonas. — Tliis is one of the commonest of soil Flagellates. The usual 
species is C. crassicauda Alexeieff, but the specific characters are not very- 
well defined, and other species such as C. longicauda may also have been 
present in some of the cultures. 
Hdteromita. — This genus is e.x.tremely abundant in all soils, commonly 
occurring in two forms which agree closely with the description of H. lens 
Miiller and H. glohosa Stein (see especially 35). The former is a small 
organism, lenticular in shape and from 4yu. to 6 ^u, in length, though some- 
times very small globular individuals occur only 2 /a or 3 /a in diameter. A 
pair of flagella arise at the anterior end, one directed forwards being about 
twice the body-length, and the other, which is normally trailed passively, 
being a little longer. The nucleus is not visible in the living animal, and 
the contractile vacuole is also not usually apparent, but when present lies 
just behind the middle. When swimming the body is turned at a sharp 
angle to the direction of motion, and the anterior flagellum lashes vigorously 
through a wide amplitude. At times the tip of the flagellum adheres to the 
glass slide, and both" flagella wave actively, so that the animal jerks vigorously 
from side to side without progressing. When stained with hsematoxylin a 
typical vesicular nucleus appears surrounded by a dense mass of peripheral 
chromatin, especially at the posterior side. The cyst is small (diameter about 
4//), thin-walled, and usually homogeneous in structure, though sometimes 
the protoplasm appears concentrated round the wall, leaving a vacuole in the 
centre, to one side of which there may be a snuil! retractile granule. 
Heteromita glohosa is larger (length 8 yu. to 12 /i), and more variable in 
shape. Usually the anterior end is rounded and the posterior end slightly^ 
narrower, but sometimes this is reversed. At times the protoplasm becomes 
quite plastic at the posterior end, which may then adhere to the glass slide 
while the anterior part moves round slowly in circles owing to the move- 
ments of the anterior flagellum. In this condition the hinder part may 
become drawn out into a long filament before the animal breaks free. The 
flagella arise together just behind the anterior extremity, the shorter one 
being about equal to the body-length and directed forwards, while the other, 
which is usually trailed passively, is about 1^ times as long. A nucleus is 
clearly visible near the anterior end, and when stained shows much less 
peripheral chromatin than in U. lens. The contractile vacuole is central. 
The movements of the body are vibratory; it is not turned outwards 
so sharply as in //. lens, and the anterior flagellum lashes through a smaller 
amplitude. The cyst has a thin outer wall which is usually raised a little 
from the thicker inner wall. The protoplasm of the cyst is hyaline, and con- 
tains a largo very retractile granule against which is a big vacuole. This 
