ARTHROPODA. 305 



animal attaches itself to some foreign body. The terminal joint 

 bears olfactory hairs, and, together with the third joint, is discarded 

 in the pupa-stage. 



b. The second appendage, a biramose swimming foot. It represents the 



second antenna of other Crustacea, but in the Cirripedia is completely 

 lost in the )//r2>-stage. 



c. The third appendage, also biramose. It represents the mandible, but 



in the adult is reduced to a toothed lobe. 



These three appendages are segmented from the first in this Cirriped. 

 In some others they are at first unjointed. The protopodites of the 

 second and third limbs bear hook-like masticatory processes. The 

 second has such a hook also in the Nauplius of Branchiopoda and 

 Copepoda. 



d. The immense labrum or upper lip. 



e. A groove on its under side (Balfour), not the oesophagus, as was sup- 



posed by von Willemoes-Suhm. 



f. Points to the unpaired dorsal eye characteristic of the Nauplius. It 



is retained throughout life in the Copepoda. In this stage it has a 

 distinct lens. Al the third moult there appears on either side of it a 

 two-jointed sense organ similar to the sense organ of the Branckio- 

 po'da, and in subsequent stages a compound eye also appears on either 

 side of it, to be lost in the pupa-stage. The two granular patches on 

 either side of the eye are the rudiments of the cerebral ganglion. 



g. The intestine. 



h. Points to the position of the anus which lies between the caudal and 

 ventral spines. These spines are at present in a compressed state 

 within the larval cuticle. The dorsal spine is developed at the third 

 moult The spines are probably a secondary adaptive protection, 

 and are not connected with the spines present in a Zoaea. 



i. The lateral processes of the cephalo-thoracic carapace to which also the 

 caudal spine belongs. These lateral processes, after the first moult, 

 are disposed horizontally outwards, and form the anterior outer angles 

 of the triangular carapace. They are hollow and give exit in an older 

 Nauplius to the ducts of glands situated under the carapace, as do 

 other shorter processes developed on the margins of that structure. 



