472 
TRANSFORMATIONS OF INSECTS. 
of the peduncle is filled up with a great mass of the egg-producing 
apparatus of the Cirripede; the ovarian tubes and the body of some 
kinds extend down into it also. On examining the attachment of 
the peduncle to the rock or timber to which it adheres, one of the 
secrets of the evolution of the Cirripede is at once discovered ; and 
the same thing occurs in investigating the adhesion of the sessile 
barnacles or acorn shells, which are so very tightly stuck on to 
stones by their shells without a peduncle. The relics of a former 
condition of life become evident, and the remains of antennae 
are discovered, which are traversed by tubes or ducts containing 
the same kind of cement which attaches the base of the peduncle 
to its supporting stone. These ducts can be followed along the 
muscles of the peduncle till they expand into the small glands 
called by Darwin — from whose admirable monograph on the 
Cirripede this description is taken — cement glands. But the 
ovarian tubes fill the peduncle more or less, and the cement 
glands are in contact with them, and the structures of the tubes 
and the glands run one into the other, and the last are, in fact, 
ovarian tubes specially modified. The cellular matter which serves 
for the development of the ova in the ovarian tubes is, by the 
special action of the walls of the gland, changed into the opaque 
cellular matter of the gland ducts, and this again subsequently 
into that tissue or substance which cements the Cirripede to its 
surface of attachment. The cement removed from the outside of 
a Cirripede consists of a thin layer of very tough, bright brown, 
transparent structureless substance, and is of the nature of chitine. 
It flowed out of the tubes traversing the antennae, and glued them 
and the neighbouring parts of the head of the Cirripede to the 
surface of the timber or stone. It becomes evident from this 
discovery that there was a previous condition of Cirripede life 
when antennae were required, and that the animal is attached by 
its head and not by a tail, and that the cirri are therefore not 
parts of the mouth or head, but are legs. A free swimming 
creature, with antennae and legs, and certainly not provided with 
a heavy shell, must have chosen a satisfactory spot whereon to 
spend the rest of its days under a very different external con- 
figuration, and must have become permanently adherent by its 
cement bearing antennae. A very remarkable metamorphosis en- 
