IV ANATOMY 83 
which live in great numbers attached to rocks and other objects 
between tide-marks, the body is constructed on a similar plan, save 
that there is no stalk, and the body is completely enclosed in a hard 
caleareous box formed from the mantle, which, when the valves 
are closed, as they always are during low tide, completely protect 
the animal inside from desiccation or danger of any kind. Besides 
the cement-glands situated in the peduncle, we can distinguish 
the generative organs, consisting of a pair of ovaries and testes, the 
majority of Cirripedes being hermaphrodite. The testes open at the 
end of an elongated median penis behind the thoracic limbs, 
tm =” 
ina 
Ys 
ee 
Sen 
gE = 
Fie. 52.—A, Dwarf male of Scalpellum vulgare, x 27; B, diagram of Stalked 
+] } ’ J z : aA 
Barnacle. a, Peduncle; ad, alimentary canal; 6, brain; c, carina; e, remains of 
: ? b ? 2 > > z 
Nauplius eye; g/, cement-gland ; im, mantle-cavity ; 0, its opening; ov, ovary ; 
5 3 > 5 > axe « 
Pp, penis ; s, seutum ; ¢, testis ; fim, tergum, seen in A as the shaded body above 
the reference-line of e and to the right of the carina, on the left of the figure. 
while the ovaries, situated in the peduncle, have paired openings 
into the mantle-cavity on either side of the head. <A pair of 
maxillary glands or kidneys are present, and the alimentary 
canal is provided with various digestive glands. Special 
branchial organs are not present in the Pedunculate Cirripedes, 
but in the Operculate genera two branchiae are formed from 
the plications of the internal surface of the mantle. There 
is no contractile heart, and the circulatory system is poorly 
developed. The Cirripedes are badly furnished with sensory 
organs; the remains of a simple Nauplius eye may persist, 
situated on the upper part of the stomach, but the chief sense- 
organs are the sensory hairs upon the limbs. 
The recent Cirripedes fall into six clearly defined Sub-orders. 
