(378 
J. DAVIDSON. 
in an antei’o-ventral direction beneath the thoracic ganglion, 
and both unite in the mid- ventral line to forma bulbous expan- 
sion in the infra-posterior region of the head. From here the 
salivary duct {s. d.) continues beneath the large pump 
muscle {m.) as a single median duct, and decreasing 
considerably in size, leads into the salivary pump (.s.), which is 
situated in the hypophai’ynx at the posterior end of the buccal 
cavity. 
The salivary glands are simple in structure (fig. 41). The 
posterior gland is a sac-like body consisting of an epithelial 
layer of large, conical cells, which bulge into the irregular 
cavity [hi.) of the sac. These cells possess fine, granular 
cytoplasm [cy.) aiid prominent, deeply staining nuclei, and 
border on the irregular lumen of the gland, which leads at 
the proximal end, by a narrow channel, into the salivary duct. 
The cells in the posterior portion of the gland appear to be 
filled with secretion, the nuclei are larger, and the cell 
contents appear less granular than in the anterior portion. 
The cell boundaries of the anterior glands are not well 
defined, and the lumen is almost entirely reduced. A few 
large, deeply staining nuclei are present, imbedded in a 
granular cytoplasm. 
The walls of the salivary duct are comparatively thick, and 
enclose an extremely fine lumen, along which the salivary 
secretion is passed. Several nuclei are seen in the walls, but 
cell boundaries are not well defined. 
The Salivary Pump. — Lying beneath the anterior end of 
the phai’ 3 mx, being supported by the small hj^popharynx, 
is the salivary pump (s.) or “ Speichelpumpe ” of German 
authors, into which the salivary duct conveys the products 
of the salivary glands, which then pass along a fine canal in 
the fused maxillae. This structure corresponds in posi- 
tion to the Wanzenspritze ” described by Wedde (1885) in 
the Rhynchota. It has been observed by Mayer (1873) 
in Pyrrhocoris, Mai’k (1877) in Chionaspis, Witlaczil 
(1882) in Aphids and Coccidae, Dreyfus (1894) in 
Phylloxera, and other authors. Krassilstschik (1892-93) 
