82 CRUSTACEA Gl RIPE At CHAP. 
Fia. 50.—Cypris-stage in the development of Lepas australis, x 15. A, Peduncle : 
A.M, adductor muscle; C, caecum of oesophagus ; O.g, cement-glands ; C7, cirri 
(thoracic appendages) ; 
E, compound eye; £', simple eye ; G, ventral ganglia ; 
J, intestine ; .W, mouth; W.C, mantle-cavity ; O, ovary; .S, stomach. (After 
Hoek. ) 
and lies free in the 
Fie. 51.—Pupa of Lepas 
pectinata, x 8. A, An- 
tenna; C, carina; J, 
adductor muscle; SS, 
scutum; JZ, tergum. 
(After Gruvel.) 
mantle-cavity, but is continuous anteriorly 
with the tissues of the peduncle, into which 
the mantle does not extend. The thorax, 
with its six pairs of legs, can be protruded 
from the mantle-cavity through the slit- - 
like opening which separates the two valves 
of the mantle along the ventral middle line ; 
and when the animal is feeding, the thoracic 
legs are so protruded, and by their concerted 
waving action they drive the food-particles 
in the water along the channel between 
them, until the particles reach the oral 
cone, where they are masticated by the 
mandibles and two pairs of maxillae, and 
so passed into the alimentary canal. When 
the animal is disturbed it rapidly retracts 
its limbs, the valves of the mantle are 
closed by means of a strong adductor muscle 
in the head, and the animal is protected 
from all external influences. In the acorn-barnacles (Operculata), 
