[12] This distinguished naturalist has given his opinion in the ‘American Journal of Science,’ March, 1846, that “the pedicel of Anatifa corresponds to a pair of antennæ in the young;” although the peduncle or pedicel is undoubtedly thus terminated, even in mature individuals, I think it has been shown that it is the whole of the anterior part of the larva in front of the mouth, which is directly converted into the peduncle. Professor E. Forbes, in his Lectures, and Professor Steenstrup, in his ‘Untersuchungen über das vorkommen des Hermaphroditismus in der Natur,’ ch. v, have considered the peduncle as a pair of fused legs. Lovén has taken, judging from a single sentence, the same view of the homologies of the external parts as I have done; in his description of _Alepas squalicola_, (Ofversigt of Kongl. Vetens., &c., Stockholm, 1844, pp. 192-4), he uses the following words: “Capitis reliquæ partes, ut in Lepadibus semper, in _pedunculum mutatæ et involucrum_,” &c.; his involucrum is the same as the capitulum of this work. As we have just seen that the first pair of natatory legs is borne on the ninth segment of the body, so it must be with the first pair of cirri, which consequently correspond to the outer maxillipods (the two inner pair of maxillipods or pied-machoires being here aborted) of the higher Crustacea, and hence their difference from the five posterior pair, which correspond with the five, ordinary pair of ambulatory legs in these same Crustacea. The part of the body, which I have called the prosoma, that is the protuberant, non-articulated, lower part of the thorax (Pl. IX, fig. 4 _n_), is a special development, either of the ninth segment, bearing the first pair of cirri, or of the segments corresponding with the organs of the mouth. The three abdominal segments of the larva are represented in the mature Cirripede, in the Order containing the Lepadidæ, only by a minute, triangular gusset, let in between the V-shaped tergal arches of the last thoracic segment: in this gusset, small as it is, is seated the anus, and on each side the caudal appendages, often rudimentary and sometimes absent. In another order, I may remark, (including, probably, the Alcippe of Mr. Hancock,) the cirri, of which there are only three pair, are abdominal.