METAMORPHOSES. 27 



seventeen segments, which, as I stated, is the full number 

 ever observed in any Cirripede, the four missing ones 

 being abdominal, and, I presume, the four terminal seg- 

 ments. That the cavity in which the thorax is lodged, 

 in the larva and therefore in the mature Cirripede, is 

 simply formed by the backward production of the cara- 

 pace, does not require any discussion. The valves have 

 no homological signification. 



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 Crus- 

 tacea, and hence their difference from the five posterior 

 pair, which correspond with the five, ordinary pair of am- 

 bulatory legs in these same Crustacea. The part of the 

 body, which I have called the prosoma, that is the protu- 

 berant, non-articulated, lower part of the thorax (PI. IX, 

 ^g. 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 Lepadidaa, 

 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 some- 

 times absent. In another order, I may remark, (includ- 

 ing, probably, the Alcippe of Mr. Hancock,) the cirri, 

 of which there are only three pair, are abdominal. 



I feel much confidence, that the homologies here given 

 are correct. The cause of their having been generally 

 overlooked arises, I believe, from the peculiar manner, 

 already described, in which the animal, during its last 

 metamorphosis, is internally almost intersected : even for 

 some little time after discovering that the larval antennae 

 were always embedded in the centre of the surface of 

 attachment, I did not perceive, that this was the anterior 



