33 
J. A. Arkwright, E. E. Atkin and A. Bacot 
forms (Plate II, fig. 6). Presumably such cells eventually rupture and dis¬ 
charge their contents into either the body cavity or the lumen of the tubule, 
but this process is not shown in any section yet examined. 
Relation of the Rickettsia bodies to the thread forms. 
Under dark ground illumination the thread forms have been observed to 
evacuate granules which, judging by their size, are similar to the darkly 
stained bodies seen within the thread forms in smear preparations. 
Circumstantial evidence suggests that these granules are the same as the 
Rickettsia bodies which in the first instance attracted our attention and that 
in bugs which have fed these bodies are largely derived from disruption of 
thread forms. 
Problem of the infection of the eggs. 
In addition to their development in certain cells of the alimentary system, 
thread forms have been found in the blood of the bug taken with a fine 
capillary pipette from the cut stump of one of the legs of a female and heavy 
infection of certain cells of the organ of Berlese has been observed in an 
apparently virgin female (no spermatozoa were observed either in this organ 
or in a smear of the ovaries which contained no developed eggs). The smear 
of the ovaries of this female also showed infection, but it was uncertain whether 
the egg cells were themselves infected. In the case of this apparently virgin 
female the form found in the sexual organs was chiefly the lanceolate form. 
The testes of the males are also infected in some cases but no signs of the 
parasite were found in smears of the accessory glands of the same insects. 
As already stated there is no evidence that the organism is motile. It seems 
possible that the eggs may be infected by the spermatozoa but attempts to 
obtain evidence from teased preparations that the spermatozoa were infected 
gave only negative results. 
General character of the infection. 
Heavy infection with this parasite must be very general, if not universal, 
among bed bugs. The stock of bugs in which the parasite was first noticed 
originated from a few specimens taken from an old Essex cottage and as the 
insects had been confined in a small box and inbred for many generations 
prior to their use for the trench fever experiments above-mentioned, it is not 
surprising that almost every bug examined showed one or other of the forms 
of the parasite. Another race was obtained from an old house situated in 
Paddington and smears were made from bugs of this stock before breeding 
from it. Insects of this stock were also found to be generally infected. A 
further supply was obtained from animal cages in a London laboratory and 
examined without giving them any chance of further feeding, 19 out of 20 
showing the presence of the parasite. 
Bugs from two different sources in Warsaw were examined within a day 
or two of capture and all these were found to be infected. 
Parasitology xm 
3 
