478 TRANSFORMATION'S OF INSECTS. 



when the pupa adheres by its antenna; to its future resting-place, 

 the skin is absorbed, and the new one does not include these organs 

 of vision. It thus happens that they are very visible through the 

 transparent shell before the last metamorphosis, which occurs at 

 the close of the pupal condition. Soon, however, these eyes lose 

 their powers ; their nerve becomes absorbed, and after a while the 

 carapace and all are moulted and cast off. 



" The eyes of Cirripcdesl' writes Mr. Darwin, "certainly undergo 

 a remarkable series of changes. In the first larva there is a single 

 eye, perhaps formed by the confluence of two, occupying the 

 normal position in the front of the head ; in the second stage the 

 eye has become double, but the two are as yet simple — they are 

 now situated posteriorly to the second pair of antennae; in the third 

 or pupal stage, they remain in the same situation, but have become 

 compound, of great size, and are attached to the bases of the 

 antennae ; in the mature or fourth stage, they have moved away 

 posteriorly, and again have become simple, of minute size, and are 

 either confluent, as in Lepas, or tolerably perfect, as in Balamis" 



It must not be supposed that the eye of the mature Cirripede is 

 metamorphosed from the eye of the pupa, for such is not the case, 

 the new eyes and the old eyes are formed some way apart, and 

 frequently both can be seen within the pupa at the same time. 



The future mature young Cirripede is gradually perfected within 

 the pupa. The mouth is formed under the rudimentary and useless 

 mouth of the pupa, and a new oesophagus is elaborated around the 

 old one. After the casting of the outer parts of the pupa, many 

 old markings are retained by the perfect creature, and it is 

 observed that the extremities of the cirri, which are so important 

 in the mature barnacle, are formed within the old legs ; moreover, 

 it is evident that the body (thorax) of the young Cirripede is not 

 formed within that of the pupa, but within a portion anterior or in 

 front of it. The position of the body becomes changed in conse- 

 quence, the alimentary canal is shortened to half its former length, 

 and the space which formerly existed between the mouth and the 

 first pair of legs is lost by coalescence. When the due time for the 

 act of metamorphosis has arrived, the carapace of the pupa splits 

 along the back, and is cast off, together with some of the segments 

 of the antenna; of the eyes and some other structures. The three 



