222 
Argas persims 
as eminently suitable for their demonstration, but a fortunate accident 
rendered this troublesome process unnecessary in our case. For some 
unexplained reason, some sections which had been stained in an alcoholic 
solution of Thionin showed a very finely granular reddish-brown pre¬ 
cipitate deposited throughout the tissues, and the cuticular canaliculi 
were most perfectly defined. 
The alimentary canal. 
For purposes of anatomical description, the alimentary canal may 
be conveniently divided into the following successive portions : 
Fore-gut. 
1. The Buccal Cavity, with 
the Salivary Glands and 
Ducts. 
2. The Pharynx. 
3. The Oesophagus. 
Mid-gut. 
4. The Stomach, with its 
coeeal appendages. 
5. The Rectum (tube com- 
municatif of Blanc). 
6. The Rectal Sac, with its 
appended Malpighian 
Tubules. 
Hind-gut. 
7. The Anal Canal 
and Anus. 
The Buccal Cavity. 
Part I, Plate V, figs. 16—18; Plate VI, fig. 21. 
The chitinous structures of the capituhim which enter into the 
formation of the buccal cavity have already received attention in the 
first portion of this paper (Part I, pp. 42-43). As there shown, the 
chelicerae and hypostome, by their apposition, form a long narrow 
tubular channel, the buccal canal {hue. can.), which terminates posteriorly 
behind the base of the hypostome in a cavity which is much flattened in 
the horizontal plane, but of considerable width from side to side. This 
space is the true buccal cavity {hue. cav.). Its roof is formed by the 
backward continuation of the cheliceral sheaths {s. ch.), while its floor is 
a direct continuation of that portion of the hypostome which forms the 
floor of the buccal canal and the hypostomal gutter {h. g.). The roof 
and floor meet and fuse together at the posterior limit of the buccal 
cavity and along its lateral margins, leaving the anterior portion open 
to the buccal canal. In the floor of the cul-de-sac thus formed, the 
pharyngeal orifice (o. ph.) opens, and the only other openings into the 
buccal cavity are situated at its postero-lateral angles, where the ducts 
of the .salivary glands {d. sal.) debouch. In transverse sections through 
