140 



FISHES. 



The gills of the Teleosteans as well as of the Ganoids 

 are supported by a series of solid cartila- 

 ginous or horny pointed rods, arranged along 

 the convex edges of the branchial arches. 

 Arches bearing a complete gill have two series 

 of those rods, one along each edge ; those with 

 uniserial gills bear one row of rods only. The 

 rods are not part of the arch, but fixed in 

 its integument, the several rods of one row 

 corresponding to those of the other, forming 

 pairs {feuillet, Cuvier) (Fig. 59). Each rod is 

 covered by a loose mucous membrane pas- 

 sing from one rod to its fellow opposite, which 

 again is finely transversely plaited, the general 

 surface being greatly increased by these plaits. 

 In most Teleostei the branchial lamellae are 

 compressed, and taper towards their free end, 

 but in the Lophobranchs their base is atten- 

 uated and the end enlarged. The mucous 



lae (magnified) of membrane contains the finest terminations 

 a,BranchofArteria of the vcsscls, which, being Very superficial, 



branchiaiis; h, ii^part the blood-rcd colour to living gills. 



Ascending branch . . p -, • -, 



of the same- c. ^^^ Arteria orancmalis, the course oi which 

 Branch of Vena lies in the Open caual in the convexity of 

 d Descending ^^^® branchial arch, emits a branch (a) for every 

 branch of the pair of lamcUse which ascends (h) along the 



same ; e, Trans- • j ri.ii 11 j t 



mner edge 01 the lamella, and supplies every 



verse section ° ' rr j 



through the one of the transverse plaits with a branchlet. 



branchial arch. rpj^^ j^^^^^ ^^^^-^ ^^ -^^^ ^ ^^^ ^^^ ^^ CapiUarieS, 



from which the oxygenised blood is collected into venous 

 branchlets, returning by the venous branch (d), which occu- 

 pies the outer edge of the lamella. 



The so-called Pseudobranchice (Fig. 60) are the remains of an 

 anterior gUl which had respiratory functions during the em- 

 bryonic life of the individuals. By a change in the circulatory 



Fig. 59. — A pair of 

 branchial lamel- 



