C. M. Wenyon 
3:>9 
Agama stellio was also found a trichomonas and a trichomastix. These are prob¬ 
ably identical with Trichomonas lacertae, Prowazek, and Trichomastix lacerlae, 
Biitschli. It is possible that if a number of Lacerta agilis had been examined 
they would have been found in them also. The Entamoeba may possibly be 
identical with one seen by Dobell (1914) in the gut of Lacerta muralis. 
Prowazekella lacertae Grassi. 
This flagellate has been the subject of some controversy on account of its 
association in the gut of the lizard with a blastocystis, or structures which 
have a striking resemblance to this. Prowazek (1904) claimed to have demon¬ 
strated that the blastocystis was in reality the autogamy cyst of the flagellate. 
It is very improbable that any autogamy takes place in the life-history of the 
flagellate, but nevertheless it is undoubtedly true that the flagellate encysts 
and that the cysts produced have frequently been spoken of as blastocystis. 
Chatton (1917) describes the blastocystis as a stage in the developmental 
cycle of the flagellate and finds that under certain conditions not well under¬ 
stood the large blastocystis resulting from growth of the smaller forms pro¬ 
duces large numbers of flagellates. He supposes, and probably correctly, that 
a conjugation between the flagellates takes place in association with the en- 
cystment. 
Description of flagellate. 
t 
The flagellate (PI. XX, Fig. 3) is in its adult stage an elongate, flattened 
organism with two tapering flagella, one of which is directed forwards and is 
several times the length of the body, and the other, a thinner and shorter one, 
directed backwards. There is a single anterior nucleus, on the anterior surface 
of the membrane of which lies a granule from which the flagella arise. 
The body of the flagellate, as already mentioned, is flattened like a blade 
of grass, but not perhaps to the same extent, and sometimes, as noted by 
Prowazek (1904), the edges are folded or the body may be twisted on itself, 
but as usually seen it is simple in structure with the posterior end pointed 
and tapering to a varying extent. The anterior end is also pointed but less 
acutely than the posterior end. The cytoplasm is vacuolated and may contain 
granules. Near the anterior end lies the spherical nucleus, which is closely 
surrounded by a number of deeply staining bodies. In iron haematoxylin 
preparations these tend to obscure the nucleus unless the differentiation is 
carried far enough. The nucleus itself is a spherical body consisting of a 
nuclear membrane and a centrally placed karyosome. Fine granules may also 
be seen within the membrane, either on its inner surface or between it and the 
karyosome. On the anterior surface of the membrane is the granule from 
which the rhizoplast arises. This granule does not retain the stain as intensely 
as the karysosome of the nucleus nor the bodies which surround the nucleus. 
In some cases it appears that the granule may be double but it is difficult to 
make out whether this is merely an early stage of division or not. From the 
