10
the cell assumes its adult form. When this position of the micronucleus is seen in a young
flagellate of the Leishman-Donovan body, it indicates that the cell has not yet reached. maturity
and that farther division is about to .take place. In my first report I drew attention to a
few instances of parasites showing this appearance, but I was not then able to explain its
significance.
A number of attenuated parasites were seen free, and in one case a thin cell containing two
chromatic dots was still attached to a small flagellate. Multiple division of the macro-and
micronuclei of the small oval flagellates takes place in the bug about the fifth day resulting in
the formation of still smaller flagellates which. are themselves capable of further longitudinal
fission. ,So far as I am aware, this process has not been seen in cultures. In the later stages
of the development of the parasite in the bug two distinct types of flagellates were seen; a
long relatively thick form measuring from 9μ to l5μ in length and 2μ to 3μ in breadth, and a
small irregular flagellate measuring from 4μ to 6μ in length and 1 μ to 4μ in breadth. In both
the micronuclei are situated about 2 μ from the anterior ends through the centre of which the
flagella pass oat.
There was no evidence to show that the thin parasites originated from the larger ones,
though Leishman has observed this process in cultures, and further, as no sexual cycle was
seen, it is not possible to say whether they represent two distinct sexes. In one of the large
flagellates (Plate II, fig. 5c )
t w o p i n k a r e a s c o n t a i n i n g a n u m b e r o f c h r o m a t i c g r a n u l e s w e r e
seen ; it is probable they represent the diplosome observed in other flagellates. In another
parasite (Plate II, fig . 6 g) there was a suggestion of a similar structure at the posterior end,
and from its vicinity a chromatic thread passed forwards and joining a similar filament termi-
nated in the flagellum. In Herpetomonas muscœ domesticœ Prowazek19 describes a spiral thread
which passes to the posterior end of the parasite and terminates in a diplosome ; prior to the pro-
-cess of copulation the diplosome divides resulting in a group of six granules. As these appear-
ances were seen only in a few of the parasites, it was not possible to follow the further changes,
if any, undergone by them.
It is hoped later to direct special attention to the final stages of the development of the
parasites and their method of re-entry into the human body.
The Bed-Bug.
The fact that the Leishman-Donovan body undergoes its extracorporeal development in the
bed-bug, Cimex rotundatus, makes it necessary to describe briefly the two species of this insect
associated with man.
According to Mr. Distant 20 the family Cimicidœ which contains four genera, Cimex,
O e c i a - c u s , C a c o d m u s
a n d
H e m a t o s i p h o n ,
b e l o n g s t o t h e H
e t e r o p t e r a ,
a s u b - o r d e r o f t h e
R h y n c h o t a ,
a n d i s
placed in the series Gymnocerta between the families Phymatidœ and Ceratocombidœ. Mr. Distant
informs methegenus Cimex at present contains four species, CimexlectulariusLinn.,cimex
rotundatus Sign, Cimex pipistrelli Jenyns21 , and Cimex columbarius Jenyns21, all of which have the
following characters : The head is short and broad with two prominent eyes, but no ocelli.
The antennæ are four jointed, the apical joints being slender ; the elytra are rudimentary and
lie over the metathorax. The prothorax is semilunar in shape with its anterior angles consider--
ably extended. The abdomen, which is uncovered, consists of seven segments and an eighth
anal appendage ; the legs are slender, the anterior tibiæ more than twice as long, and the
posterior three times as long, as the tarsi, which are three jointed. The proboscis is flexed in
a ,groove beneath the head and prothorax.
Type species Cimex lectularius Linn. The adult insect of this species is reddish brown in
colour and is covered with fine hairs ; it varies in length from 4 . 5 to 5 millimeters, the male
usually being a little smaller than the female. The head is short and broad and is inserted into
a notch in the prothorax ; it contains two lateral prominent eyes in front of which are the two
antennæ and in the median line the thick first segment of the labrum which is continuous with
the dorsal integument of the head. The antennae consists of four segments, the first two being
the thicker, while the third and fourth are slender and covered with long hairs.
The prothorax is semilunar in shape with two rounded horns extending close up to the eyes ;
its upper surface is raised in the centre and towards the sides, ending abruptly at a line a little
beyond the level of the eyes ; the remainder of the surface including the two horns is flattened
from above downwards. The ventral surface of the prothorax is concave and hollowed out on
each side of the mid-line where the first pair of legs are inserted. The mesothorax as seen from
the dorsal surface is triangular in shape with its apex projecting over the metathorax and
between the elytra. The metathorax next in size to the prothorax is almost entirely covered
on its dorsal side by the elytra, and on the ventral surface is seen as a small cleft on the inner
side of the middle coxa. The elytra which are inserted into the mesothorax just below the
lateral angles are two rudimentary scallop-shaped pieces of' chitin lying over the metathorax
and sides of the first abdominal segment. Their dorsal surfaces are convex and covered with
bristles, while their ventral surfaces are concave. The abdomen is rounded and consists of
seven segments with an eighth anal appendage. It is broadest at the third segment and