METAMORPHOSES. 25 



the body of the larva ; and, as the whole has to be rejected 

 or moulted, the membrane of the peduncle of the young 

 Cirripede has necessarily to be formed with a wide and 

 deep inward fold, extending transversely across it ; this 

 when stretched open, after the exuviation of the larval 

 carapace and apodemes, necessarily causes the sternal 

 side of the peduncle to be longer than the dorsal, and, 

 as a consequence, gives to the young Cirripede its normal 

 position, at right angles to that of the larva when first 

 attached. 



I may here state, that I have examined the larva 3 in 

 this the final or perfect stage in four species of Lepas, in 

 Conchodermavirgata, Ibla quadrivalvis, and, though rather 

 less minutely, in Balanus balanoides, and I find all 

 essential points of organisation similar. With the excep- 

 tion of diversities in the proportional sizes of the different 

 parts, and in the patterns on the carapace, the differences, 

 even in the arrangement of the spines on the limbs and 

 antennae, are less than I should have anticipated. 



I have in this abstract treated the metamorphoses at 

 greater length than I should otherwise have done, on 

 account of the great importance of arriving at a correct 

 homological interpretation of the different parts of the 

 mature animal. In Crustacea, according to the ordinary 

 view, there are twenty-one segments ; of these I can re- 

 cognise in the Cirripede, on evidence as good as can 

 generally be obtained, all with the exception of the four 

 terminal abdominal segments ; these do not occur in any 

 species known to me, in any stage of its development. 

 If that part of the larva in front of the mouth, bearing the 

 eyes, the prehensile antennae, and in an earlier stage two 

 pair of antennae, be formed, as is admitted in all other 

 Crustacea, of three segments, then beyond a doubt, from 

 the absolute correspondence of every part, and even every 

 coloured mark, the peduncle of the Lepadidae is likewise 

 thus formed. The peduncle being filled by the branch- 

 ing ovarian tubes is no objection to this view, for I am 



