130 
Herpetomonads in Mice 
tapered to the opposite or posterior end which was often pointed (Figs. 
1-5). The movements of the organism were very active and jerky. 
Violent contraction of the body together with vigorous lashing of the 
flagellum could occur. The flagellum was relatively rigid at its basal 
end near the body, the rest lashed freely and spiral codings of the 
flagellum were frequently seen, while backward bending was sometimes 
noticed. The flagellum functioned as a tractellum, as it dragged the 
body after it. There was no undulating membrane. 
The bodies of the flagellates were Up, to 18p long and about 3p to 
4p broad at the widest part. The flagellum was about equal to or 
slightly greater than the body in length. The nucleus, as seen by 
intra vitam staining, was approximately centrally situated. The 
blepharoplast was refractile and often barlike in life. Anteriorly a 
refractile area was sometimes present, which was apparently the 
flagellar sac of some authors, the flagellum seeming to be partially 
retracted into it at times. 
Partial formation of the non-flagellate stage of the parasite was 
sometimes observed. Kegression of the flagellum accompanied by 
cytoplasmic concentration resulted in the assumption of an elongate 
oval resting form (Figs. 6, 7). 
It may be added that no especial ectoparasites were found on the 
mice, but they were kept in laboratories where rats and rat-fleas, 
Ceratophyllus fasciatus and CtenophtJialmus agyrtes, were also present. 
The latter fleas came of a stock known to be infected with Crithidia 
ctenophthahni. It is very likely that the former flea was infected with 
Herpetomonas ])attoni, as such fleas in England are known to harbour 
scanty infections of this parasite. The non-flagellate stages of Crithidia 
and Herpeto7nonas are indistinguishable. 
We have succeeded in introducing Herpetomonas jacitlum, H. pedicvli, 
H. ctenophthalmi, and Crithidia gerridis into vertebrates such as mice 
and dogs by feeding or inoculation. We have also shown that cold 
blooded vertebrates like sticklebacks, frogs, toads, lizards and snakes 
can be infected with these insect flagellates. These results are recorded 
in two papers read before the Cambridge Philosophical Society on 
November 23rd, 1914, and May 10th, 1915. Thus we see that what 
can be induced artificially in the laboratory can occur also in Nature. 
Since the above observations were made, one of us, while working 
in Liverpool, has been much interested in some remarks by Dutton 
and Todd (1903) relating to researches made in 1902 on the Gambia. 
These workers record the presence of Herpetomonas in the blood of house 
