] The testes are
small, often leaden-coloured, either pear or finger-shaped, or branched
like club-moss,--these several forms sometimes occurring in the same
individual; they coat the stomach, enter the pedicels, and even the
basal segments of the rami of the cirri, and in some genera occupy
certain swellings on the thorax and prosoma, and in others the
filamentary appendages: the testes seen in the apex in one of these
appendages in Conchoderma, is represented in Pl. IX, fig. 5. The two
vesiculae seminales are very large; they lie along the abdominal surface
of the thorax, and generally (but not in some species of Scalpellum)
enter the prosoma, where their broad ends are often reflexed; here the
branched vessels leading from the testes enter. The membrane of the
vesiculae seminales is formed of circular fibres; and is, I presume,
contractile, for I have seen the spermatozoa expelled with force from
the cut end of a living specimen. The two canals leading from the
vesiculae generally unite in a single duct at the base of the penis; but
in _Conchoderma aurita_, half-way up it. The probosciformed penis,
except in certain species of Scalpellum, is very long; it is capable of
the most varied movements; it is generally hairy, especially at the end;
it is supported on a straight unarticulated basis, which in _Ibla
quadrivalvis_ alone (Pl. IV, fig. 9 _a_), is of considerable length; in
this species, the upper part is seen to be as plainly articulated as one
of the cirri; in Alepas, the articulations are somewhat less plain, and
in the other genera, the organ can be said only to be finely ringed, but
these rings no doubt are in fact obscure articulations. In the females
of _Ibla Cumingii_ and _Scalpellum ornatum_, there is, of course, no
penis.

[18] In 'Mueller's Archiv,' 1834, p. 467. I have already several
times referred to M. Martin St. Ange's excellent Memoir, read
before the Academy of Sciences, and subsequently, in 1835,
published separately.

_Female Organs._--M. Martin St. Ange has described how the peduncle[19]
is gorged with an inextricable mass of branching ovarian tubes, filled
with granular matter and immature ova. In Conchoderma and Alepas, the
ovarian tubes run up in a single plane (Pl. IX, fig. 3,) between the two
folds of corium round the sack. Here the development of the ova can be
well followed: a minute point first branches out from one of the tubes;
its head then enlarges, like the bud of a t