BARNACLES 251 
mouth of the animal, which is dependent upon such food as comes 
within range of its tentacles. 
Their life-history is interesting. The young barnacle, called a 
nauplius, in no way resembles the adult. When it emerges from 
the egg it is a free and independent animal, with one eye, three 
pairs of legs, and a single shell. It 
swims about for a while and moults 
m several times. It then has two eyes, two 
@ shells, and six pairs of legs. At this 
period it seeks a permanent home, and 
attaches its anterior end to the object it 
selects by means of its antenne, which 
HE have become suckers. It makes its hold 
Balanus. A, external view: s, Secure by secreting a cement which 
ee permanently fastens it to the spot. It 
then undergoes metamorphosis, loses its bivalve shell and its 
eyes, and attains its characteristic cirripeds, or curled feathery 
legs, and a new shell covering. During these transformations, 
from the time it be- 
comes fixed until it at- 
tains its adult form, 
the barnacle fasts, liv- 
ing by the absorption 
of its own animal fat. 
Its food subsequently 
consists of the minute 
animal forms which 
abound in the sea. Its 
further growth is by 
moulting, but parts 
only of its covering 
are disengaged; the 
shellis permanent, and Balanus. B, anatomy : a, antennules; ad, adductor muscle ; m, 
its successive stages PUT°tcutum, sr parapet; f orgum; wo, female aperture. 
of growth are marked , ; ; 
upon it by lines, as in mollusks. The lining of the shell, or en- 
veloping skin of the animal, and also the cuticle of the legs are 
