218 Mr Harrison, A preliminary account of the 
the relaxation of the digastric muscles and contraction of all three 
pairs of retractors it is returned to its normal resting position. 
Method of feeding. =] 
The method of feeding may now be briefly recapitulated. When 
the louse has selected a spot, the haustellum is protruded by pro- 
traction of the buccal plate, and a superficial fixation effected by 
the buccal teeth. The same action brings the buccal tube into 
contact with the skin, and the contained piercing apparatus enters 
the tissues of the host, and penetrates to the level at which blood 
is reached. Salivary secretion accompanies the piercer, and possibly 
contains an anti-coagulin and also has some solvent action. The 
pumping-pharynx commences its rhythmical dilatations, by means 
of which blood is drawn in through the buccal tube, and passed 
backwards to the pharynx, where, by means of alternate contrac- 
tion of the sphincters and dilatation by the dilatators, it is pumped 
backwards into the oesophagus, by the peristaltic action of which 
it is carried to the stomach. 
At the close of the feeding process, the piercer is drawn in by 
its own retractors, the retractors of the labium serving to pull the 
sheath back. The retractors of the buccal cavity draw in the 
haustellum and buccal tube. 
The fundamental error in Schiddte’s classic experiment of 
cutting off the anterior part of the head of a louse during feeding 
is that it severs the piercer from its retractors, and it is thus 
-shown as protruding for a distance which is impossible in view of 
the short ‘pitch’ of these muscles. The second error was, of course, 
the assumption that this ‘tube’ was the channel through which 
the blood passed. 
Interpretation. 
In the absence of ontogenetic work proving beyond doubt the 
homologies of the various structures described, any interpretation 
will depend primarily on the view taken of the affinities of the 
Anoplura. Enderlein (1904), being satisfied that these insects are 
hemipterous, has been able to homologise the parts contained 
within the piercer-sheath as labium, hypopharynx, and maxillae, 
corresponding to those of the Rhynchota. Cholodkowsky (1904), on 
the other hand, states definitely from embryological etl, that 
mandibles and maxillae disappear, and that the piercer-sheath and 
its apparatus are formed from the labium alone. He expresses his 
conviction that the Mallophaga and Anoplura are closely related, 
and includes them in a new order, Pseudorhynchota, an unnecessary 
proceeding seeing that several names, eg. Anoplura Leach and 
Parasita Latreille, already exist for a combination of the two 
groups. As the Mallophaga are undoubtedly of orthopterous 
