ns untwist and are
withdrawn and the bodies separate, to crawl up the suspending
cord and depart.

Some snails have a special organ for creating sexual excitement.
A remarkable part of the reproductive system in many of the true
Helicidae is the so-called _dart, Liebespfeil_, or _telum
Veneris_. It consists of a straight or curved, sometimes
slightly twisted, tubular shaft of carbonate of lime, tapering to
a fine point above, and enlarging gradually, more often somewhat
abruptly, to the base. The sides of the shaft are sometimes
furnished with two or more blades; these are apparently not for
cutting purposes, but simply to brace the stem. The dart is
contained in a dart-sac, which is attached as a sort of pocket to
the vagina, at no great distance from its orifice. In _Helix
aspersa_ the dart is about five-sixteenths of an inch in length,
and one-eighth of an inch in breadth at its base. It appears most
probable that the dart is employed as an adjunct for the sexual
act. Besides the fact of the position of the dart-sac
anatomically, we find that the darts are extended and become
imbedded in the flesh, just before or during the act of
copulation. It may be regarded, then, as an organ whose functions
induce excitement preparatory to sexual union. It only occurs in
well-grown specimens. (Rev. L.H. Cooke, "Molluscs," _Cambridge
Natural History_, vol. iii, p. 143.)

Racovitza has shown that in the octopus (_Octopus vulgaris_)
courtship is carried on with considerable delicacy, and not
brutally, as had previously been supposed. The male gently
stretches out his third arm on the right and caresses the female
with its extremity, eventually passing it into the chamber formed
by the mantle. The female contracts spasmodically, but does not
attempt to move. They remain thus about an hour or more, and
during this time the male shifts the arm from one oviduct to the
other. Finally he withdraws his arm, caresses her with it for a
few moments, and then replaces it with his other arm. (E.G.
Racovitza, in _Archives de Zooelogie Experimentale_, quoted in
_Natural Science_, November, 1894.)

The phenomena of courtship are very well illustrated by spiders.
Peckham, who has carefully studied them, tells us of _Saitis
pulex_: "On May 24th we found a mature female, and placed her in
on