516 



ANATOMY OF VERTEBRATES. 



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 

 Newts, the side-slits are 

 longer retained. The 

 young of CcBcilia 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 

 disappear, the branchial 

 arches adhere to the oper- 

 cular fold of skin, the 

 external outlet being an 

 inferior transverse slit. 



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

 orifices become obliterated after the absorption of the internal 

 gills. The gigantic Newt of Japan (Cryptobranchus) equally 

 differs from Mcnopoma and Amphiuma in the closure of those 

 orifices. Their retention in these large American Newts, with 

 the superadded persistency of the branchiae themselves in Meno- 

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

 evidences of the manifestation of generic characters through 



The internal branchios of the Tadpole of the Frog, magn. 



CCLXV1II. 



stages 



of 



one 



general 



course of transmutatioual 



arrested 

 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, running along the antero-inferior border : they there send off 

 a double series 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. 343. From this the returning 



