METAMORPHOSES OF CIRRIPEDES. 127 



carapace separates, all round the orifice, from the delicate 

 tunic lining the sack and investing the thorax and natatory 

 legs of the pupa ; for these membranes are not moulted for 

 some considerable time afterwards. Hence all these inner 

 parts retain for a period the appearance and structure of the 

 natatory pupa, whilst the exterior resembles, in every respect, 

 a fixed and perfect Cirripede. 



In my former volume, I have insisted on the important 

 and curious results which ensue from the eye-apodemes 

 penetrating so deeply into the body (see PL 30, fig- 7, in 

 which the proportions are more correct than in fig. 2), with 

 the eyes attached exteriorly to their outer arms ; for as these 

 apodemes have to be ejected, the external membrane of the 

 young Cirripede (PL 30, fig. 2) has to be formed in a deep 

 fold or arch over them, and consequently the membrane on 

 the sternal surface is formed considerably longer than on 

 the dorsal surface. From this it follows, when all the mem- 

 branes are free and are stretched fully out after the moult, 

 that the whole animal, posteriorly to the cementecl-doAvn 

 surface, turns vertically up, and assumes its normal position 

 at right angles to the surface of attachment, and to that 

 which it held in its pupal condition ; for the pupa always ad- 

 heres with its sternal surface parallel to the surface of attach- 

 ment. A young Lepas, which has just moulted its pupal 

 carapace, and has assumed its proper vertical position, with 

 the cemented antennae and the surface of attachment remain- 

 ing as before, is shown at fig. 3, but is drawn on a smaller 

 scale than the pupa fig. 2, out of which it may be supposed 

 to have been excluded. In this fig. 3, it may be observed 

 that the natatory legs and caudal appendages of the pupa 

 have not as yet been moulted. The fact of the stretching 

 out, in the young Cirripede, of the fold of membrane, which 

 in pupa, just before the metamorphosis passes over the 

 apodemes and eyes, is well shown by three darkly-coloured 

 bands in the corium, which in the pupa are curled, but after 

 the moult, are stretched straight out on the peduncle of the 

 young Lepas. 



The pupa, and consequently the young Cirripede, from 

 being attached at first by the antennas, does not adhere by the 

 actual anterior extremity, but by the sternal surface near it ; 



