368 Herpetomonas jaculum (Leger) 
a species of which this paper is chiefly concerned, has one of its 
members connected with the disease known as Kala-azar in India, 
while the parasites of infantile splenomegaly and of Oriental sore are 
also developmental stages of Herpetomonads. In the case of Kala-azar, 
the adult flagellates have been seen to develop in the bed-bug, Cimex 
rotundatus. 
The subject of this paper is, however, not a pathogenic agent, so far 
as I am aware, but lives, apparently harmlessly, in the alimentary tract 
of the water-scorpion, Nepa cinerea. The flagellate stage of the parasite 
was first described by Ldger in 1902, and was named by him Herpeto¬ 
monas jaculum. In this paper I hope to give, for the first time, the 
complete life-history of the parasite. 
Material and Methods. 
The “common” water-scorpion does not appear to be so common 
nowadays as its name would imply. Though many likely localities in 
the south-east of England have been tried, yet the majority failed to 
yield specimens of Nepa cinerea. However, many adults and a fairly 
large number of nymphs were obtained. Most of the Nepa were 
infected with the Herpetomonas. Specimens have been examined at 
all seasons of the year. It is only in the nymphs of Nepa that the pre¬ 
flagellate stages can be examined with any degree of ease. 
Each Nepa was carefully dissected 1 and the intestine removed. This 
was divided into portions which were teased in physiological salt 
solution, and the parasites were fixed wet either by osmic vapour or 
the vapour of strong formalin, both of which were efficient, the osmic 
fixation being perhaps slightly the better. The preparations were then 
spread, without being allowed to dry. Preparations of the ovaries were 
made in the same way. Cover-glass smears were sometimes made. 
Most of the smears were treated throughout by the wet method, while 
others were allowed to dry before being stained. Other preparations 
were made in which Bouin’s liquid and corrosive-acetic-alcohol were 
used as fixing agents. 
For observations in vivo hanging-drop preparations were used, or 
else preparations of the infected gut in a little physiological salt 
solution were placed under a cover-slip, the edges of which were sealed 
1 During my investigations I have seen various stages, especially spores, of the 
Coccidium, Barroussia ornata (A. Schneider), in the gut-epithelium and Malpighian 
tubules of Nepa cinerea. 
