er Cirripede, and I believe it is nothing but the tissue,
here not calcified, which, in a calcified condition, ordinarily forms
the valves. On this view, the males may be said to be lodged in pouches,
formed in the thickness of the valves.

_Concluding Remarks._--The males from the absence of a mouth (and no
doubt of a stomach), must necessarily be short-lived, and, I suppose,
are periodically replaced by fresh males.[57] In one instance, the
remnants of the two great compound eyes of the larva, could be seen at
the end of the pouch, opposite the orifice. The larvae, I conclude, crawl
in at the orifice, one side of which is formed, as we have seen, of
yielding membrane, and scratch out the dead exuviae of the former
occupant: certainly, the males are less firmly attached to their
pouches, though some small quantity of cement is excreted, than are
other Cirripedes to the objects to which they are attached. The small
size of the female, and her valves not being thickly edged with chitine,
accounts for the males having pouches specially formed for them, instead
of being, as in _S. vulgare_, laterally imbedded in the chitine-border
of the scuta. In hereafter weighing the evidence on the nature of the
parasites in Ibla and in Scalpellum, the fact of the valves of the
supposed female being here modified for the special purpose of lodging
the males, will be seen to be important. If we imagine the male
parasites to be extraneous animals, and that by adhering to the sack of
the Scalpellum, they injure the corium and thus prevent the growth of
the shell over an area exactly corresponding to their own size, and so
form for themselves cavities; yet what can be said regarding the
preparatory furrows? surely these narrow lines cannot have been produced
by the pressure of the much broader parasites. Must we not see in the
furrows, the first marking out, if such an expression may be used, of
the habitation for the male, which has to be specially formed by the
independent laws of growth of the female?

[57] It is possible, though opposed to all analogy, that the
females may be short-lived, and breed only once, in which case
the males would not have to be periodically replaced.

3. SCALPELLUM RUTILUM. Pl. VI, fig. 2.

_S. (Foem. an Herm.) valvis 14 sub-rufis: carinae tecto plano, utrinque
crista rotundata instructo; margine basali truncato: lateribus
superioribus latitudine duplo longioribus._

(Fem. or Herm.) Capitulum w