496 CIRRIPEDIA. 



equivalent to the second pair of maxillae, and give rise to the 

 third pair of jaws in the adult (sometimes spoken of as the 

 lower lip). 



Behind these appendages there are moreover formed the rudi- 

 ments of six pairs of feet. Under the cuticle of the first pair of 

 antennse there may be seen just before the final moult the four- 

 jointed antennae of the Cypris stage with the rudiment of a disc 

 on the second joint by which the larvae eventually become 

 attached. 



By the free Cypris stage, into which the larva next passes, a 

 very complete metamorphosis has been effected. The median 

 and paired eyes are present as before, but the dorsal shield has 

 become a bivalve shell, the two valves of which are united along 

 their dorsal, anterior, and posterior margins. The two valves 

 are further kept in place by an adductor muscle situated close 

 below the mouth. Remains of the lateral horns still persist. The 

 anterior antennae have undergone the metamorphosis already 

 indicated. They are four-jointed, the two basal joints being 

 long, and the second provided with a suctorial disc, in the centre 

 of which is the opening of the duct of the so-called antennary or 

 cement gland, which is a granular mass lying on the ventral 

 side of the anterior region of the body. The gland arises 

 (Willemoes Suhm) during the Nauplius stage in the large upper 

 lip. The two distal joints of the antennae are short, and the 

 last of them is provided with olfactory hairs. The great upper 

 lip and second pair of antennae and mandibles have disappeared, 

 but a small papilla, forming the commencement of the adult 

 mandibles, is perhaps developed in the base of the Nauplius 

 mandibles. The first pair of maxillae have become small papillae 

 and the second pair probably remain. The six posterior pairs 

 of appendages have grown out as functional biramous swimming 

 feet, which can project beyond the shell and are used in the 

 locomotion of the larva. They are composed of two basal 

 joints, and two rami with swimming hairs, each two-jointed. 

 These feet resemble Copepod feet, and form the main ground 

 for the views of Claus and others that the Copepoda and 

 Cirripedia are closely related. They are regarded by Claus as 

 representing the five pairs of natatory feet of Copepoda, and the 

 generative appendages of the segment behind these. Between 



