234 
Argas per stem 
colour, derived from the undigested detritus which remains within its 
lumen. After engorgement, the coecal lobes become so distended and 
crowded together, that it is a difficult matter to recognise the different 
parts. 
The oesophageal opening of the stomach is situated at the anterior 
end of its ventral portion, immediatel}^ behind the point where the 
latter bifurcates to form the antero-lateral lobes. The rectum originates 
in a corresponding position at the posterior end of the stomach, where 
it commences as a funnel-shaped depression of the ventral wall (see 
Pis. XIV and XV, t. c.). 
The stomach wall consists of two la 3 'ers—an inner epithelial la 3 ’er 
and a very thin outer muscular layer—the latter appearing to be more 
or less embedded in the delicate homogeneous membrana propria upon 
which the bases of the epithelial ceils rest. The epithelial sti’ucture 
varies very considerably in the different phases through which it passes, 
prior to and after engorgement. In unfed individuals the epithelial 
cells are cylindrical, and though they may vary somewhat in size, they 
show a complete uniformity in structure throughout the entire viscus. 
After engorgement, the epithelium becomes thicker, and here and there 
individual cells become elongated so as to protrude into the lumen of 
the organ beyond the general surface of the stomach wall (see PI. XVII, 
fig. 2). These pseudopod-like protrusions of the epithelium assume 
a more or less spherical form, but alwa 3 ?s remain attached to the base¬ 
ment membrane by their now pedunculate bases. The nuclei of these 
epithelial cells, which, in unfed individuals, are situated near the 
basement membrane, move towards the free margins of the cells and 
take up their position in the protruded spherical extremities. The cell 
contents also undergo considerable changes. Before engorgement, the 
cytoplasm is finely granular and, as mentioned above, the nuclei are 
situated near the bases of the cells. After engorgement, and while 
active digestion is in progress, the proximal portions of the cells develop 
a very striking reticulate structure, and the distal portion of each cell, 
more particularly those which have elongated to form the pseudopodial 
protrusions, become densely packed with large spherical granules which 
are deeply stained by the acid dyes. Whether these spherical granules 
represent the secretory product of the epithelial cells or not, is doubtful, 
for after digestion has proceeded for a time, similar granules appear 
within the body cavity, suspended in the blood-serum, and are even 
found ingested by the amoeboid blood corpuscles. This seems to in¬ 
dicate that the acidophile granules are the actual nutrient products 
