e sides of the same
individual. As males in other classes of the animal kingdom often retain
some female characters, so here (though the case is not strictly
analogous[50]) the male possesses the cementing apparatus, which
homologically is part of an ovarian tube modified.

[50] Certain plants offer a closer, though not perfect, analogy.
Thus, in the florets of some compositous flowers, the pistil,
besides its proper female functional end, serves to brush the
pollen off the anthers; while, in the florets of some other
compositae (see the account of Silphium in 'Ch. K. Sprengel Das
entdeckte Geheimniss der Natur'), the pistil is functionless for
its proper end, the flower being exclusively male, but its style
is developed, and still serves as a brush. So in the male Ibla,
part of the ovaria, in a modified condition, is still present,
and serves as a cementing apparatus.

The individuals in every other genus (with the exception of Scalpellum),
in the several families, in the three Orders of Cirripedia, are
hermaphrodite or bisexual. Why, then, is Ibla unisexual; yet, becoming,
in the most paradoxical manner, from its earliest youth, essentially
bisexual? Would food have been deficient, and was the seizure of
infusoria by another and differently constructed individual, necessary
for the support of the male and female organs? The orifice of the sack
of the female is unusually narrow; would the presence of testes and
vesiculae seminales have rendered her thorax and prosoma inconveniently
thick? Seeing the analogous facts in the six, differently-constructed
species of the allied genus Scalpellum, I infer there must be some
profounder and more mysterious final cause.

2. IBLA QUADRIVALVIS. Pl. IV, fig. 9.

ANATIFA QUADRIVALVIS. _Cuvier._ Mem. pour servir ... Mollusq.
1817, Art. Anatifa, Plate, figs. 15, 16.

IBLA CUVIERIANA. _J. E. Gray._ Annals of Philosophy, vol. x, New
Series, Aug. 1825.

---- _J. E. Gray._ Spicilegia. Zoolog. Tab. iii, fig. 10.

TETRALASMIS HIRSUTUS. _Cuvier._ Regne Animal, vol. iii, 1830.

ANATIFA HIRSUTA. _Quoy_ et _Gaimard_. Voyage de l'Astrolabe, Pl.
xciii, figae. 7-10, 1834.

_I. (Herm.), valvis et pedunculi spinis sub-flavis: basali tergorum
angulo, introrsum spectanti, hebete, quia margo carinalis inferior
longius quam margo scutalis prominet._

_Hermaph._--Valves and spines on the peduncle yellowish: basal angle of
the t