CIRIUPEDIA. 283 



are two dorso-lateral channels in the prosoma, which are in direct 

 connection with the great main channel, running down the ventral 

 side of the peduncle. This latter main channel branches out in the 

 lower part, and transmits the blood through the ovai-ian tubes, whence, 

 I believe, it flows upwards and round the sac, re-entering the body 

 near the sides of the adductor scutorum muscle. The main ventral 

 channel, in the uppermost part of the peduncle, has a depending 

 curtain, which, I think, must act as a valve, so as to prevent the 

 circulating fluid regurgitating into the animal's body during the 

 contractions of the peduncle."* 



In the pedunculated Cirripeds slender appendages, which from 

 their position and connections are homologous with the branchiae of 

 the higher Crustacea, are attached to, or near to, the bases of a 

 greater or less number of the thoracic feet, and extend in an opposite 

 direction, outside the visceral sac. In the common Barnacle (^Lepas 

 anatiferd) there are two pairs of such branchias; the first {d, fig. 121), 

 is attached to the side of the prosoma, anterior to the first cirrigerous 

 foot, and seems to answer to the gill developed from the last 

 maxillary foot in the lobster ; the second appendage {d) springs from 

 the dorsal surface of the swelling (^) at the basal joint of the first 

 thoracic foot. In the Lepus fascicularis I find one gill attached to 

 the prosoma, and three others radiating from the base of the first 

 thoracic leg.f In the Olion there are two gills from the side of the 

 prosoma, and five from the bases of the first five thoracic legs ; seven 

 pairs in all, most of which are unusually long and tapering. With 

 respect to the function of these appendages, I concur with Mr. Darwin 

 in deeming them of very secondary importance in respiration, having, 

 like him, always found them occupied by lobes of the testis. The 

 extensive vascular surfaces of the corium and of the body-sac, ex- 

 posed to the sea-water, with the active cirri themselves, most probably 

 suffice for the aeration of the blood; and the additional expansion of 

 surface, afforded by the plicaled tubular appendages to the body of 

 the Otion, concurs to effect the same end. The homologues of the 

 branchial appendages of the Barnacles are not present in the Balanids ; 

 the respiratory function is here especially aided by the production of 

 plicated folds of the body-sac, which are very numerous and complex 

 in the Coronula diadema."^ 



The Cirripedia are hermaphrodite : there are no known exceptions 

 to this rule in the sessile order : in the pedunculated one a few ex- 

 ceptions have been discovered by Darwin, e. g. Ibla Ciimmiugii 

 and Scalpellum oniatum, in which the large attached individuals 



* CCXXIII. p. 4C. t Pi<;l>- No. 994. % Prep. No. 997. 



