ecific forms by causes
acting on the animal while battling with its fellows in the struggle for
existence, and perhaps consider that the metamorphoses of the animal
within the egg are due to a reflex action of the modes of life of the
ancestors of the animal on the embryos of its descendants.

[Illustration: 125. The Turkey Louse.]

FOOTNOTES:

[Footnote 5:

Ha! whare ye gaun, ye crowlin ferlie!
Your impudence protects you sairly:
I canna say but ye struift rarely,
Owre gauze and lace;
Tho' faith, I fear ye dine but sparely
On sic a place.

Ye ugly, creepin, blastic wormer,
Detested, shunn'd by saunt and sinner,
How dare ye set your fit upon her
Sae fine a lady!
Gae somewhere else and seek your dinner
On some poor body.

(To a Louse.--Burns.)]

[Footnote 6: We notice while preparing this article that a journal of
Parasitology has for some time been issued in Germany--that favored land
of specialists. It is the "Zeitschrift fur Parasitenkunde," edited by
Dr. E. Hallier and F A. Zurn. 8vo, Jena.]

[Footnote 7: Figure 111 represents the parts of the mouth in a large
specimen of _Pediculus_ vestimenti, entirely protruding, and seen from
above, magnified one hundred and sixty times; aa, the summit of the head
with four bristles on each side; _bb_, the chitinous band, and _c_, the
hind part of the lower lip, such as they appear through the skin by
strong transmitted light; _dd_, the foremost protruding part of the
lower lip (the haustellum); _ee_, the hooks turned outwards; _f_, the
inner tube of suction, slightly bent and twisted; the two pairs of jaws
are perceived on the outside as thin lines; a few blood globules are
seen in the interior of the tube.]

CHAPTER X.

THE DRAGON FLY.

Were we to select from among the insects a type of all that is savage,
relentless, and bloodthirsty, the Dragon fly would be our choice. From
the moment of its birth until its death, usually a twelve-month, it
riots in bloodshed and carnage. Living beneath the waters perhaps eleven
months of its life, in the larva and pupa states, it is literally a
walking pitfall for luckless aquatic insects; but when transformed into
a fly, ever on the wing in pursuit of its prey, it throws off all
concealment, and reveals the more unblushingly its rapacious character.

Not only do its horrid visage and ferocious bearing frighten children,
who call it the "Devil's Darning-needle," but it even