120 BALANlDiE. 



inflected inwards, and their corners are produced far up into 

 the body, thus forming the curious UU-like apodemes. 

 These apodemes exist throughout the whole class ; and the 

 outer arms always carry the great compound eyes. I 

 noticed, in Lepas pectinaia, that the two middle arms are 

 proportionally longer than in L. amtralis. Owing to the 

 presence of these apodemes, and to certain coloured marks 

 on the adjoining corium, the eyes, though inclosed fairly 

 within the carapace, yet deceptively appear pedunculated, 

 so that even J. Vaughan Thompson was thus deceived. 

 I have alreadv described the several muscles attached to these 

 apodemes, and the constant vibratory movement of the eyes. 

 Whilst the pupa remains a freely swimming animal, the 

 eyes are included, not only within the shell or carapace, but 

 (as would naturally happen) within the corium or true skin 

 lining the carapace , but after the pupa has become attached, 

 preparatory to its final metamorphosis (in the state repre- 

 sented at PL 30, fig. 2.), not only are the muscles, as before 

 remarked, which are attached to the apodemes, absorbed, 

 but so is the corium investing the apodemes and the imme- 

 diately adjoining parts of the carapace. Hence it comes 

 that the new corium of the young Cirripede within, is formed 

 in a deep transverse fold across the whole lower half of the 

 animal, and the apodemes with the eyes are thus, as it were, 

 rejected from within the corium, though still remaining 

 within the carapace. Consequently in this final stage, the 

 eyes and apodemes are very conspicuous from the outside, 

 being seen only through the transparent carapace. I pre- 

 sume that the eyes at this period have become functioniess, 

 with the optic nerve divided and absorbed. The eyes, 

 apodemes, and carapace soon afterwards are all moulted 

 together. 



The eyes of Cirripedes certainly undergo a remarkable 

 series of changes : in the larvae in the first stage, there is a 

 single eye, perhaps formed by the confluence of two eyes, 

 occupying the normal position in the front of the head : in the 

 second stage, according to Burmeister, 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 



