D. L. MACKINNON 
289 
for his kindness in putting the material at my disposal, and to the 
Carnegie Trust, from which I received a research grant during my work 
in Cambridge. 
The material for dissection consisted of 29 adult fleas taken from 
three moles’ nests supplied from Tring Park, through the courtesy of the 
Hon. N. C. Rothschild. The nests were sent to the laboratory on the 
9th of February. I did not begin dissection until the 23rd of February, 
and the last infected flea was found on the 20th of March : I record this 
fact, because it shows that the fleas had been long without food, and 
that therefore the possibility of the parasites’ having come from infected 
mole-blood was small. 
Of the twenty-nine fleas examined, four were found infected with 
flagellates. 
The method of observation of the parasites was very simple. The 
digestive tract of each flea was dissected out in a drop of normal salt- 
solution, and examined under a objective. If there were any parasites 
present, the flagellates could always be made out inside the gut, moving 
in a peculiar jerky manner, aptly described by Balfour as resembling 
that of the agitated needle of a compass. Parasites were never seen in 
the mid-gut. They were chiefly congregated in the expanded upper 
portion of the hind-gut into which the malpighian tubes open. They 
could also be seen in little groups lower down ; frequently the gut was 
slightly dilated at these points. The cysts, though usually present in 
the rectum, could not be seen in the living state, owing to the opacity 
of the large rectal glands. I much regret that scantiness of material 
prevented my making a proper study of the living parasites. 
When the flagellate had been located, the gut was divided into three 
portions, and smeared on a slide. In three instances the smears were 
then dried, and fixed in absolute alcohol. I obtained a better result 
with my last specimen, which I fixed in the manner recommended 
by Swingle, i.e. fix with vapour of 40 °/o formalin for 10 minutes, and 
then wash off any superfluous salt with warm water: after that, I fixed 
further in alcohol for 10 minutes. All the preparations were stained 
with Giemsa’s stain. 
I. Herpetomonas ctenophthalmi, n. sp. 
Three fleas were infected. One belonged undoubtedly to the species 
C. agyrtes ; the other two were either C. agyrtes or G. bisoctodentatus. 
Parasitology n 19 
