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 neighbouiing parts of the Jicad 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- 



