224, Mr Harrison, A preliminary account of the 
have the same general relations as those described by Enderlein ; 
for Haematopinus. Mjsberg (1910, p. 205) figures them also for 
Antarctophthirus, in which they are conspicuous even in the adult. — 
In the later larval stages of Pediculus these mandibles gradually — 
disappear. If these structures be not mandibles, as the double 
muscular attachments would suggest, they are difficult to account | 
for. They are certainly functionless. Against. such an inter-— 
pretation is the fact that they lie in the haemocoele. Here 
Cholodkowsky’s account of the growth forward of a fold of the 
ventral integument to cover the labium, which is drawn inwards 
in the invagination of the piercer-sheath, suggests an explanation. — 
The mandibles may also be involved in this process of epiboly, 
and, by the subsequent absorption of the upper wall of the fold, 
become internal. An intermediate condition actually occurs in — 
the Mallophagan genus Philandesia, in which the mandibles are — 
almost completely shut off by two lateral folds of the ventral 
surface of the head. 
Tn any case the mandible and maxilla may be dismissed as far 
as any participation in the actual mouth-parts of the Anoplura is 
concerned. Cholodkowsky states that the piercing apparatus is 
formed entirely from the labium. As the labium in Mallophaga 
is reduced to a sub-mentum and mentum, with rudimentary, one- 
jointed palps, it 1s impossible to believe that all the structures 
involved could be derived from labium alone. I suggest that the 
two plates lying in the floor of the piercer-sheath may represent 
the sub-mentum and mentum. 
The buccal tube and the piercing apparatus are thus left un- 
accounted for. I believe that the whole of these structures have 
been derived from modifications of the Mallophagan hypopharynx. 
The figures of Cummings (1913) show the remarkable fluidity of 
this structure and the variation it has undergone even in closely 
allied species. The piercer-sheath is a depression in the floor of 
the buccal cavity, into which opens a pair of apparently function- 
less glands, as well as the salivary duct, in all of which it agrees 
with the Mallophagan hypopharynx. Moreover this suggestion 
affords a means of homologising the buccal tube, which otherwise 
is difficult to account for. It is comparatively easy to picture the 
two halves of this tube as the anterior cornua of the hypopharynx, 
which lie above, and lateral to, the central depressed portion ; and 
also to imagine the latter drawn backwards into the long piercer- 
sheath, this invagination involving the associated parts. It would 
be idle, in view of the speculative nature of the suggestion put 
forward, to attempt to press the homologies still further, and to 
try and indicate the precise origin of the dorsal and ventral 
plercers. 
The buccal plate and teeth do not demand any particular 
