courtship is slow and elaborate. It has been described by James
Bladon ("The Loves of the Slug [_Limax cinereus_]," _Zoölogist_,
vol. xv, 1857, p. 6272). It begins toward midnight on sultry
summer nights, one slug slowly following another, resting its
mouth on what may be called the tail of the first, and following
its every movement. Finally they stop and begin crawling around
each other, emitting large quantities of mucus. When this has
constituted a mass of sufficient size and consistence they
suspend themselves from it by a cord of mucus from nine to
fifteen inches in length, continuing to turn round each other
till their bodies form a cone. Then the organs of generation are
protruded from their orifice near the mouth and, hanging down a
short distance, touch each other. They also then begin again the
same spiral motion, twisting around each other, like a two-strand
cord, assuming various and beautiful forms, sometimes like an
inverted agaric, or a foliated murex, or a leaf of curled
parsley, the light falling on the ever-varying surface of the
generative organs sometimes producing iridescence. It is not
until after a considerable time that the organs 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withdrawn and the bodies separate, to crawl up the suspending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
Helicidæ 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