A. Pouter 
245 
dogmatic hypotheses of certain writers, G. pulicis would be a stage of a 
trypanosome. No trypanosome has ever been observed in my blood, 
whether examined by smear, thick film or culture, and this examination 
has been frequently made by highly competent authorities. Further, 
the extended period over which observations have been made is sufficient 
to put this supposition entirely out of court. 
Again, no sore of any kind has ever developed on my body, though 
bites of the usual chai'acter have been made by the Ideas repeatedly. 
These observations exclude all possibility of C. pulicis being a stage 
or stages in the life-cycle of other flagellates, such as those described by 
C. Basile, and effectually dispose of the wild hypothesis laid down by a 
would-be authority, that flagellates of sanguivorous insects must be 
regarded as stages in the life-cycle of a vertebrate trypanosome. 
Also, I have thought it well to investigate fleas from outside sources, 
and through friends, to whom my best thanks are due, obtained fleas 
from several places in each of the following counties;—Sussex, Surrey, 
Hampshire, Gloucestershire, Wiltshire, Somerset, London, Lancashire, 
Cambridge and Essex. Some of the fleas from each of the above-named 
counties contained G. pulicis. In every case, the parasites presented 
identically the same morphology and life history as those obtained from 
my bred Pulex. Recentljq a criticism {Bull. Sleeping Sickness Bureau, 
May, 1911) was made of a paper by Swingle on the transmission of 
T. lewisi by rat-fleas, in which the critic “presumes” that the fleas used 
were “wild” fleas, and adds:—“in the present state of our knowledge, 
in the case of flagellates found in wild insects, it is almost guesswork to 
say that certain forms are natural flagellates and others stages of blood 
trypanosomes.” Considering the evidence that is steadily accumulating 
of the occurrence of natural flagellates in blood-sircking insects, the 
above statement seems a rash and inexact one. Bruce and his col¬ 
leagues have recently shown that natural flagellates, Grithidia, occur 
in the sanguivorous Tabanid flies suspected of transmitting Trypano¬ 
soma pecorum, and that the Grithidia are flagellates of the insects and 
not developmental forms of a trypanosome. Wild insects include 
sanguivorous and non-sanguivorous forms; while the case of “wild” 
insects feeding on plants is obviously overlooked. 
As far back as 1906, Ross published on Grithidia in mosquitos in 
India (observed between 1895 and 1899) and in connection therewith 
stated (p. 107) “ In fact, it was evident that they [Grithidia^ had been 
already present in the insects before these were fed on the blood.” The 
sanguivorous habit of an insect is no criterion as to whether a flagellate 
