516 



ANATOMY OF VERTEBRATES. 



.r( s^a 



)Vj, 





Teleostomous Fishes, especially of the Lophobranchs ; and the 

 analogy to the piscine respiratory structures is enhanced by the 

 growth of an opercular fold of membrane, protecting the branchial 



chamber; but this, by pro- 

 "■•■' gressive adhesion of its 



posterior border to the cer- 

 vical integument, reduces 

 the lateral fissures to one 

 inferior foramen. In the 

 Xewts, the side-slits are 

 longer retained. The 

 y(3ung of CiEcUia show a 

 branchial pore on each 

 side, with traces of bran- 

 chial fringes. The embryo 

 Salamander shows exter- 

 nal gills while ' in the 

 womb ; and, when these 

 disa])pear, the branchial 

 arches adhere to the oper- 

 cidar fold of skin, the 

 external outlet beino; an 

 inferior transverse slit. 

 In Newts, Salamanders, Ca3cilia3, and Anourans, the branchial 

 orifices become obliterated after the absorption of tlie internal 

 gills. The gigantic Newt of Japan (Cn/ptohranchus) equally 

 differs from Menopoma and Amphiuma in the closure of those 

 orifices. Their retention in these large American Newts, with 

 the superadded persistency of the brancliire themselves in Minio- 

 branchus, Siren, and Proteus, are amongst the most significant 

 evidences of the manifestation of generic characters through 

 arrested stages of one general course of transmutational 

 developement. 



§ 91. Arteries of Reptiles. — In the Axolotl, fig. 344, the three 

 anterior pairs of vascular arches rise distinctly from the ' bulbus,' 

 A ; the fourth pair blend their origins with those of the third : 

 the three anterior pairs are, functionally, branchial arteries, ib. B, 

 course along the corresponding branchial arches to the sides of 

 the neck, and then quit them to enter the base of the pendent 

 gill, nmning along the antcro-infcrior border : they there send off 

 a double scries of branches, which penetrate and ramify in the 

 branchial fringes, and constitute at their end and margin'a capil- 

 lary net-work, like that in fig. 34.3. From this the returning 



The iiiternixl liraiichite of the- TaOpole of tbe Frog, magn. 

 CCI.XVIII. 



