THE Hog LovusE 689 
in a common duct for a short distance before entering the middle of the 
dorsal surface of the piercer sheath by a common openirig, while in 
Haematopinus eurysternus she describes them as running separately to 
the opening into the salivary duct of the mouth parts. Peacock (1918: 
115) refers briefly to Martin, and to a dissection made by Mr. Lloyd, 
Chief Entomologist to N. Rhodesia, as demonstrating that the four 
salivary ducts open into the bulbous structure at the posterior end of 
the chitinous salivary tube. 
Of these interpretations that of Sikora is probably the most accurate, 
because it alone describes an arrangement of the ducts which allows of 
their being drawn forward by the mouth parts during feeding without 
danger of their rupture. 
Patton and Cragg (1913:559) describe a small collection of round cells 
surrounding the esophagus and constant in position, which differ from 
the cells of the fat body in their more glistening appearance. They dis- 
tinguished no duct with certainty, though in some dissections a fine filament, | 
which may have been a duct, was seen passing upward with the salivary 
duct. Miller (1915) discusses these cells in connection with the fat 
body, but remarks that up to that time no fat has been demonstrated in 
them. Harrison (1916 b:220) says that in the Siphunculata (Anoplura), 
groups of specialized binucleate cells, richly tracheated, lie about the 
ducts of the salivary glands, at the base of the esophagus. Sikora (1916: 
57-58) gives a detailed account of the structure and appearance of these 
cells, which she calls “ grosszellige Driisen,” in Pediculus vestimenti, 
and mentions their presence in the other species investigated. She 
considers them as quite distinct from the fat cells and suggests that they 
withdraw some constituent from the body fluid and store it or act on it 
in some way before returning it to the body fluid. 
In the hog louse there is a cluster of small, subcircular cells, arranged 
like a pair of wings, lying above the base of the esophagus. Between 
these cells and the esophagus pass cephalad the dorsal vessel and the 
ducts of the salivary glands. On dissection each half of the cluster is 
found to consist, on the average, of forty small cells united by a network 
of very fine tracheoles. The two median posterior cells, which are some- 
what larger than the others and pear-shaped, lie side by side on the end 
of the esophagus with their pointed ends caudad, and from each of them 
a slender tracheole passes to the surrounding network of the fat cells 
