838 
[May 2, 
hypopliaryiix ai)i)ear.s to lie above the base of tlie mandibles, but 
below that of the maxillary jjalpi. 
The true relations of this unpaired organ undoidjtedly need 
further elucidation, but at 2)resent I am inclined to take the view 
that it is the homologue of the hypoi^harynx of Diptera, the 
point deciding me being the fact that, as m Diptera, it contains 
the efferent duct and opening of the salivary glands which in all 
other insects is situated in the hypoj)harynx or in a homologous 
portion (tongue, lingua, "spinneret" of caterpillars) of the second 
maxillae. 
Fig. 23. yl, portion of the inoiith-parts of Fulex erinacei ; hyp, hj'po- 
pharynx ; can, place where the salivary canal enters between the styles of 
the hypopharynx; B, a, h, end of the hypopharynx with a portion of the 
mitldle highly niagnilied showing its gutter-lilie shape. — Author del. 
The identification of the hard parts is rendered peculiarl}' 
difhcult in the Siphonaptera owing to the unusual shape of the 
head, which is without a labrum or epipharynx, a loss due to 
adaptation to its suctorial habits and semiparasitism ; and to the 
unusual position of the base of the mandibles and maxillae, 
though as Avill be seen by the sections of Kraepelin and of 
Wagner the hyj)opharynx is embraced by the mandibles, and lies 
immediately over the labium, this being the normal position of 
the hypopharynx of other iu'Sects. 
In order to bring out with exactness the tru(> nature of the 
bypophar^Mix of Diptera and other insects, I will give a brief 
r6sum6 of the knowledge of this unpaired organ, which is the 
