THE CIRRIPEDIA. 
4 77 
sea-weed and other objects, are in reality the altered large antennae 
of the larva of the first stage ; but the smaller antennae have wasted 
away. The eye has commenced becoming double, but is not as 
yet compound in structure. The mouth is still in the form of a 
proboscis, and does not differ much from its former condition. 
Ru.t no jaws or mouth-pieces are present. The legs are still in 
three pairs, the mouth bears the same relation to them as before, 
and the abdomen has become short. 
Considerable increase in size takes place during the development 
of the Cirripede up to the time when it is about to enter the third 
larval state, which, from its having some peculiarities, that will 
be noticed hereafter, is more or less correctly termed the pupal 
condition. 
On comparing the larva of the second stage and the pupa, no 
very great external changes can be discovered ; but the great 
antennae have come out of their surrounding cases, the carapace 
has extended so as to enclose the whole body, the eyes have 
become further apart, and three other pairs of legs have been 
developed behind the others. Moreover, a small abdomen has 
become slightly separated from the thorax. The mouth, formerly 
a proboscis, and active enough in swallowing and seizing, is now 
closed and functionless ; but its position is marked by a sort of lip, 
the old shrivelled oeosphagus, and the commencing jaws and new 
gullet. This mouthless pupa can swim rapidly, but it does not 
appear to have much, if any, power of steering itself, and it 
differs in these peculiarities from the larva, for that could swim 
where it chose, and with considerable energy. The pupa of one 
species of Lepas can walk tolerably over sea-weed with the aid 
of its large antennae ; and these are formed of four segments, those 
nearest the body supporting the eyes. The position of the cement 
tubes with respect to the antennae of the perfect Balanus has 
been already noticed. They may be traced in the pupa to end in 
a third and disc-shaped segment, which is used as a climbing 
structure. The cement constantly exudes from the outside of the 
disc, and finally it causes the antennae to adhere permanently. 
Whilst the pupa remains a free swimmer, the eyes, the position 
of which to the antennae has been noticed above, are included within 
the carapace or shell, but they are within the skin lining it. But 
