274 ZOOLOGY 
The head bears one pair of antennae, the first. Its second 
joint bears a disk on which the duct of the cement gland opens. 
In Lepas and Balanus this appendage is minute, and situated 
at the base of attachment. The cement gland lies in the stalk 
of the stalked forms, its secretion hardens into a cement which 
serves to attach the animal to some foreign body. 
The second pair of antennae, although present in the larva, 
are thrown off at the last moult, and are therefore not found in 
the adult. Above the mouth is an upper lip or labrum, and 
on each side of it is a mandible; between the mandible and 
the labrum is a structure called the palp, which, however, is 
not the homologue of the ordinary Crustacean palp. There 
are two pairs of maxillae, the posterior pair being fused together 
to form a kind of labium. 
The thorax bears six pairs of appendages, the biramous 
nature of which recalls the limbs of the Copepods (Fig. 163). 
The rudimentary abdcmen has no appendages, it terminates in 
a long penis, which is usually bent forward between the thoracic 
legs. 
The mouth leads by a short oesophagus into a globular 
stomach provided with certain hepatic diverticula ; the intestine 
passes off from the stomach and ends in a short rectum. The 
anus is situated dorsally at the base of the penis. 
In addition to the hepatic diverticula certain glands have 
been described lying near the stomach, with which they com- 
municate by a duct on each side. These glands secrete a fluid 
which has probably some digestive action, they have been 
termed pancreatic glands, formerly they were described as 
ovaries. 
The Cirrhipedia seem to be devoid of any special circulatory 
apparatus. The space between the internal organs-of the body 
is largely filled up with connective tissue, but certain cavities 
occur which seem to be lined by an endothelium, and which 
have been regarded as truly coelomic. Into these spaces a pair 
of ducts open by means of funnel-shaped orifices. These 
ducts have been traced in one or two genera, and have been 
found to open on to the exterior at the base of the second maxilla, 
the appendage which bears the aperture of the Entomostracan 
excretory organ, the shell gland. These tubes are believed to 
