ON A NEW PATHOGENIC LOUSE 
5 
enter, two on either side, close together. Immediately beyond the malpighian 
tubules, a distinct dividing line between the mid-gut and the intestinal epithe- 
lium is seen. 
The intestine is straight and thin-walled, but there is no differentiation 
into large and small intestine. The intestine passes from the muscular pyloric 
mass, close beneath the abdominal terga, to the rectum. The cells lining the 
cavity are small ; there is a layer of circular muscle fibres, and outside this a 
number of longitudinal fibres. The nuclei of the latter form conspicuous 
objects in the fresh tissues. The rectum consists of a distended globular 
portion, containing rectal papillae, and a straight narrow portion leading 
directly to the anus at the apex of the gth segment. 
Salivary Glands. — These are small oval structures, consisting of a 
single acinus, which rests upon the anterior portion of the mid-gut in the 
first abdominal segment. A duct, which is of delicate structure, leads for- 
wards towards the pharyngeal pump. Each acinus consists of several large 
cells with a central clear space, which is very refractile. 
Malpighian tubules. — These resemble the tubules of insects generally 
and consist of cells with large oval nuclei. The cells are much drawn out, 
and nuclei are situated at considerable intervals along the tube. 
Generative organs. — The female organs consist of an ovary on each side, 
opening into a short common oviduct. Each ovary is composed of 5 or 6 
follicular tubes. Each follicular tube is attached to the body wall by a 
delicate apical strand of tissue, and opens into the oviduct of its own side. 
Each follicular tube contains two or more egg follicles in different stages of 
development. In the adult louse two fully matured follicles, one lying on 
each side, largely fill up the abdomen. All, except the youngest follicles, 
consist of a single layer of cubical or columnar cells surrounding an ovum 
and nurse cells. In the mature follicles the nurse cells, which lie towards the 
apex of the follicle, have become absorbed. 
S-permatheca. — This is a large, thin-walled, chitinous sac, opening by a 
short tube near the anus. It may be empty or contain masses of sper- 
matozoa. 
Male organs. — The testes are curious double peg-top shaped organs. 
Each opens by a narrow tube into a wide seminal vesicle, in which masses of 
spermatozoa are seen. The duct of the testis opens at a distance from the 
end of the seminal vesicle, so that this possesses a caecal extremity. The 
seminal vesicle lie across the abdomen and open together into a short, 
straight tube surrounded with large muscle nbres. This tube in turn passes 
into the penis. 
The fat body. — This is well developed. In the head and thorax it forms 
pads lying between the muscles and the organs. A very conspicuous pad 
lies beneath the pharynx, and other masses are situated close to the salivary 
glands. In the abdomen, the fat body consists of a number of conical 
masses attached by their apices to the body wall, near the origin of the 
lateral hairs. The bases of the conical masses lie against the mid-gut and 
other viscera and give support to these. The cells which compose the fat 
