the Rhizocephala, i.e. the tubules which penetrate from its point of
adhesion into the body of the host, ramify amongst the viscera of the
latter, and terminate in caecal branchlets. In the pupae of the
Rhizocephala (Figure 58) the foremost limbs ("prehensile antennae")
bear, on each of the two terminal joints, a tongue-like, thin-skinned
appendage, in which we may generally observe a few small strongly
refractive granules, like those seen in the roots of the adult animal. I
have therefore supposed these appendages to be the rudiments of the
future roots. A perfectly similar appendage, "a most delicate tube or
ribbon," was found by Darwin in free-swimming pupae of Lepas australis
on the last joints of the "prehensile antennae." From the perfect
accordance in their entire structure shown by the pupae of the
Rhizocephala and Cirripedia, there can be no doubt that the appendages
of Sacculina and Lepas, which are so like each other and spring from the
same spot, are homologous structures.

Now in three species of Lepas, in Dichelaspis Warwickii and in
Scalpellum Peronii, Darwin saw, on tearing recently-affixed animals from
their point or support, that a long narrow band issued from the same
point of the antennae; its end was torn away, and in Dichelaspis,
judging from its ragged appearance, it had attached itself firmly to the
support. From this it follows that this appendage in Lepas australis can
hardly be anything but a young cement-duct. If, therefore, the
supposition that the appendages on the antennae of the pupae of
Rhizocephala are young roots be correct, the roots of the Rhizocephala
are homologous with the cement-ducts of the Cirripedia. And this,
strange as it may appear at the first glance, seems to me scarcely
doubtful. It is true that the act of adhesion of the Rhizocephala has
never yet been observed, but it is more than probable that they attach
themselves, just like the Cirripedia, by means of the antennae, and that