402 



ANATOMY OF VERTEBRATES. 



326 



altijjenuis, Lactttrius delicatulus). Corvina trispinosa, fig. 326;, lias 

 two slender caical processes from each side of its air-bladder ; the 

 Bearded Umbrina has three such processes ; the 

 allied ' Maigre ' and other species of Sciasna, 

 with most of the CorvincB, have very numerous 

 lateral pneumatic cajca, which, as in Johnius 

 lohatus, fig. 327, are more or less ramified.' In 

 some species of Cheilonemus and Gadus blind 

 processes are continued from both the sides and 

 ends of the air-bladder (see the anterior ones 

 in Gadus callarias, fig. 321, A, p). In Gadus 

 Navavarja. the lateral productions expand, and 

 line corresponding expansions or excavations of 

 the abdominal parapophyses, thus foreshadow- 

 ing the pneumatic bones of birds. In Kvrtus the 

 air-bladder is encircled by expanded ribs, curvi)ig 

 and meeting below it.' 



The proper walls of the air-bladder of ordi- 

 nary Osseous Fishes consist of a shining silvery 

 fibrous tunic, the fibres being arranged for the 

 most part trans-\'erscly or circularly, and in two 

 layers fig. 229, q r; they arc contractile and elastic; but 

 the walls of the anterior compartment of the air-bladder of 

 Cyprinoids, ib. p, are much more elastic than 

 those of the posterior one. The air-lJadder 

 is lined by a delicate mucous membrane, with a 

 ' plaster epithelium ;' it is more or less co\cred 

 by the peritoneum. Its cavity is commonly 

 sim])le ; in the iSheat-fish it is divided by a 

 vertical longitudinal septum along three-fourths 

 of its posterior part.-' The lateral compart- 

 ments arc subdivided by transverse septa in 

 mtuiy other Siluroids (e. g. genus Barp-Ks) : the 

 large air-bladder of some species of En/fhrimis 

 (c. g. E. salvus, E. twniaf/is) is partially subdi- 

 vided into smaller cells. Tiie cellular subdivi- 

 sion is such in the air-bladder of the Amia, that 

 Cuvicr compared it to the lung of a reptile' ; 

 M<-hi:„M.r..ini,i,h,.,M,„i,^3 and the transition from the air or swim-bladder 



' XXXIX. i. p. 0-1, after Ciivicr anil Valinicicnncs, xxin. ]il. 138, l."9. Tho most 

 iMimplcx form is that descrihcil l>y GiiiitlH-r (or.xxiv, vol. ii. p. ni:Miii C',illic/il/ii/s 

 liicliki, wlicro the air-l)laiUlcr forms a secoml invcsliiiciU of llic ahdoiiiiiial viscera, 

 witliin lliu pcritoiiouin. 



= CLxsiv. vol. ii. p. lu. •' oxvi. vol. ii. (.. as, pi. 0, tig. I. ' XXIV. vol. ii. p. 377. 



327 





