102 
Psyche 
[December 
ends are fused to the exoskeleton of the head on either 
side of the orifice, while its middle part is connected to 
the medial side of the glandular opening. When the muscle 
is relaxed, the flap lies just beneath the lateral edge of the 
orifice, and thus separates the orifice, which lies medial to 
it, from the glandular opening, which is lateral to it (Fig. 
4). When the muscle contracts, the flap is pulled over to 
just beneath the medial side of the orifice; the glandular 
opening then lies immediately below the orifice, and the 
secretion can escape through the latter (Fig. 5). 
The wall of the gland is very smooth and delicate, and 
appears silvery in freshly dissected specimens. Its histology 
was examined in serial sections through the heads of two 
fifth-instar nymphs and three adults of Gelastocoris; the 
material was fixed in 'Carnoy’s or alcoholic Bouin’s, pre- 
pared for sectioning by means of the Peterfi method, and 
stained in either Mallory’s triple connective-tissue stain or in 
Delafield’s hematoxylin and eosin. Text-figure 1 shows the 
general appearance of the glandular epithelium in an adult 
specimen. It is comprised of a simple layer of cells with 
no suggestion of an acinar arrangement. The most con- 
spicuous elements are the large cells, which are usually 
flat in adult gelastocorids but appear more cubiodal or 
cylindrical in the nymphs. These cells probably produce the 
secretion. Their large nuclei are about 15 p in diameter, 
and contain conspicuous nucleoli and many chromatin 
granules of various sizes. The cytoplasm is homogeneous 
and deeply staining in adults but appears more vacuolar in 
nymphs. An intracellular canaliculus with striated walls 
penetrates the cytoplasm of each large cell ; it seems to run 
across the cell in an obliquely transverse direction, opening 
onto the lumen of the gland usually near the lateral bound- 
ary of the cell. 
The lumen of the gland is lined by a delicate chitinous 
intima, which does not appear to penetrate into the canali- 
euli. Lying along the intima or between the intima and 
the large cells are small spindle-shaped nuclei, whose cyto- 
plasm is either very sparse or absent; their greatest dia- 
meter ranges between 5 and 10 p. In many parts of the 
epithelium the large cells are absent, and only the in- 
