40 - Drs Fantham and Porter, Some Insect Flagellates 
occurred in some cases. The experiments of these authors tend 
certainly to support the hypothesis that the flagellates parasitic in 
the blood of mammals originated in insect hosts, and also show | 
the possibility that other flagellates, equally ranked as harmless 
to the Metazoa, may acquire pathogenic properties when introduced 
into strange hosts. 
In order to test whether this were so, a series of experiments | 
was undertaken by us during the past year. While Laveran and | 
Franchini often used nearly associated insects and vertebrates, eg. 
rat-fleas and rat or mouse, dog-fleas and dog, we made a wide 
divergence, in order to ascertain whether an insect flagellate intro- 
duced into a quite unassociated vertebrate might become pathogenic. 
For this purpose, Herpetomonas jaculum (Léger), parasitic in. the 
“water scorpion,” Vepa cinerea, was chosen as the flagellate, while 
very young mice served as vertebrate hosts. We also succeeded 
in infecting a puppy by feeding it on parasitised dog-fleas. 
II. The Lofe-cycle of HERPETOMONAS JACULUM in 
NEPA CINEREA. 
Herpetomonas jaculum, parasitic in the alimentary tract of 
Nepa cinerea, is a flagellate possessing also a non-flagellate stage 
in its life-cycle. This non-flagellate form is an ovoid, Leishmania- 
es eee ete + eee 
like resistant body that is passed from the host with the faeces. © 
If the excrement so infected be ingested by another Nepa, these ~ 
resistant, oval, post-flagellate forms have their firm, varnish-like 
coat dissolved by the digestive juices of the host, and become 
capable of further development. Such forms are known as pre- 
flagellates. The pre-flagellates in the stomach of the Nepa 
gradually elongate. <A flagellum arises near the blepharoplast, 
reaches the surface of the body at the anterior end and projects as 
a free flagellum. 
By elongation of the posterior end of the body, the full, typical 
flagellate form is produced. Multiplication of the parasite occurs 
by longitudinal binary fission in both the pre-flagellate and 
flagellate stages. As the organisms pass onwards into the intes- 
tine, the environment is less favourable and they react accordingly. 
The body cytoplasm becomes concentrated, the flagellum is with- 
drawn and largely dissolved, and the now compact, more or less 
oval parasite secretes a varnish-like coat for itself, becoming thus 
-the post-flagellate form again; in which condition it passes from 
the host. The life-history of H. jaculuwm in its insect host was 
fully described and illustrated by one of us in 1909. . 
While the anterior part of the gut of the Nepa, consisting of 
oesophagus and stomach, contains mostly pre-flagellate and young 
flagellate forms, the posterior gut consisting of the intestine 
