on the Structure of the Mouth in Pediculus. 223 
provided, which is both the largest and the most easily obtainable 
of the species living on the human body (I got mine from the 
workhouse), it will be advisable to let them hunger for three or 
four days. It is only with repugnance that one thinks of put- 
ting one of them on one’s hand; but at last we summon courage, 
and soon the purely scientific situation from which to view the 
matter—man and his parasite—is obtained. Scarcely does the 
abominable little monster feel the heat of the skin before it lays 
aside its former disheartened attitude, and begins to feel at ease, 
its antennze oscillate for joy, and it stretches all six legs com- 
placently out from the body. But, though the pleasure and 
surprise at the sudden transportation into congenial sur- 
roundings for the first moment eclipsed everything else, hunger 
soon asserts its claim, sharpened as it is by the long fast which 
has rendered its stomach and intestines quite transparent. The 
animal raises itself on its legs, walks on a few steps, seeking 
and feeling its way with its antennee, while we follow it with 
the magnifier. Presently it stops, draws in its legs a little, 
arches its back, bends the head down towards the skin at an 
oblique angle, while it pushes a small dark and narrow organ 
repeatedly forward, and draws it back through the fore end of 
the head; at last it stands still, with the point of the head 
firmly abutted against the skin. We seize the animal with a 
forceps and attempt to detach it loosely from the skin, whereby 
an appreciable, though of course weak, resistance is perceived 
before it lets go its hold with the head; we expect to see a pro- 
truding haustellum, but there is nothing to be observed*. We 
then leave the animal to its own devices, and it at once resumes 
the former position. Quite a new spectacle then presents itself. 
discrimination between the two species, to take into consideration the 
sexual differences, which are not meonsiderable, and which are not quite 
the same in both species. Burmeister says that the legs are slenderer in 
P. vestimenti, and attempts to illustrate this difference by means of 
Nitzsch’s figures; but I cannot discover it in the animals themselves ; nor 
does it appear to me correct to describe the second joint of the antennz 
as elongated in P. vestimenti, although I grant that the first two joints 
seem to be a little longer in that species than in P. capitis; but if these 
small differences are to be of use, the two species must be defined with far 
greater accuracy than hitherto. 
* Swammerdam speaks of similar attempts with the same result. “ But 
my object was to see the haustellum so much the clearer when I removed 
the louse from its place, in which, however, I never succeeded; so that at 
times I almost wished I had been able to use three hands, in order to in- 
vestigate this more accurately, though there are several kinds of dissections 
and investigations which do not admit of a second person being present, 
which, besides, distracts the attention.” (Biblia Nat. i. p. 79, quoted by 
ahs ,snetion in Dutch, but translated for the convenience of the English 
reader.) 
