14 CIRRIPEDIA, 



The thorax in two of the Orders bears no appendages, 

 but in all common Cirripedes it is furnished with six pairs 

 of biramous, multiarticulated cirri, wdiich have a peculiar 

 character, different from the limbs of other Crustaceans, 

 not being natatory, ambulatory, or branchial, but "captorial" 

 or fitted for sweeping the water, and thus catching prey.* 

 The cirri,, at least the anterior pairs, can, besides other 

 movements, lengthen and shorten themselves ; and this Milne 

 Edwardsf states is the case with the Podophthalmia, and is 

 considered by him as an important character. The cirri of 

 the first pair are attached on each side close to the bases 

 of the mandibles, and, as already remarked, have some claim 

 to be considered as maxillipeds or mouth organs. The three 

 or the four posterior pairs of cirri in the Balanidae, form a 

 series somewhat distinct from the two or three anterior pairs, 

 thus recalling a characteristic feature in the Edriophthalmia. 



The mouth is prominent, and is formed by the partial 

 confluence of the labrum, palpi, and lower segments of the 

 mandibles, and of two pairs of maxillae ; it is capable of 

 movement as a whole ; in this respect we are reminded of 

 the Suctorial Entomostracans ; but I believe the above type 

 of structure of the mouth is peculiar to Cirripedes. 



The alimentary canal is simple, but can be distinctly 

 divided into — (1st) an oesophagus, singular from the bell- 

 shaped expansion of its lower end ; (2d) the stomach, 

 which is directed forwards and then doubled back ; and 

 (3d) the rectum. There is no distinct liver. The circula- 

 tion is lacunal. In one family there are well-developed 

 branchiae, which differ entirely in their homologies and 

 position from these organs in all other Crustaceans. In the 

 nervous system, the sub-cesophageal ganglions vary in 

 concentration from that degree observed in the lower 

 Macroura, to that in the highest Brachyoura ; but the supra- 

 cesophageal ganglions are always much less concentrated, 

 and are even embryonic in condition ; presenting a difference 

 not observed in other Crustaceans. On the under side of the 

 sub-cesophageal ganglion, two nerves, apparently splanch- 



* M. A. Hancock, in ■ Annals and Magazine of Natural History,' 2d series, 

 1849, p. 312, speaks of the cirri acting like a prehensile net. 

 | c Annales des Sciences Nat.,' torn, xviii, p. 121, 1852. 



