in tite Fcetus of Vertehrated Animals. 109 



there are only three branchial arteries formed on ea^h side of 

 the neck by the subdivision of the aorta ; each of these vessels 

 gives a branch to one of the gills. The arteries of the head and 

 neck are derived from the branchial veins or vessels which carry 

 back the blood which has passed through the gills, and from 

 communicating vessels passing between the arteries and veins 

 at the roots of the gill stalks. The pulmonary artery is given 

 off at the place where the posterior branchial artery and vein 

 meet and join with the anterior ones to form the roots of the de- 

 scending aorta. 



From the drawing of the Amphiuma Didactylus by Dr Poc- 

 kels, published by Rusconi (which Cuvier has shewn was erro- 

 neously taken by these anatomists for the siren), it appears that 

 the distribution of the branchial arches in this animal resembles 

 more that of the larva of the salamander, there being four 

 branchial arteries, the three anterior of which supply the gills, 

 while the posterior, a fourth, alone is ramified on the sac of the 

 lungs.* 



(To he concluded in our next.) 



Explanation of the Plates. 



In all the figures, the following letters indicate the different parts : — 



a, The ventricle. a\ The auricle of the heart. 5, The bulb of the aorta. 

 b\ The ascending aorta, c. The liver, rf, The stomach, rf', The oeso- 

 phagus. Cj The mouth, e'^ The anus. /, The eye. ^, The anterior. 

 g^y The posterior extremities. H, The external gills, the stalks. A, The 

 leaflets. I, The internal gills or branchial plates, t, The leaflets or 

 fringe, x, The operculum, k^ The rectum and cloaca. L, The lungs. 

 /, The cellular part, /', The trachea, m, The branchial vascular 

 arches, n, The returning vessels or branchial veins, o, The branchial 

 apertures, p, The pulmonary arches or arteries, r, The left ; r', The 

 right root of the descending aorta. *, The descending aorta, t. The 

 carotid artery, m, The brachial, and in Figs. 9 and 11 the mammary. 

 IT, Communicating vessels of the branchial arches which are obliterated, 

 r. The urinary bladder and allantois. a?, The artery of the yolk. i/. 

 The vein carrying blood to the yolk, y, The returning vein of the yolk. 

 », The umbilical artery, y, The umbilical vein. ^, Ductus arteriosus. 



• For a farther account of these animals, see Configliachi and Rusconi 

 Del Proteo Anguino di Laurenti Monografia. Pavia, 1819, of which an 



account is given by D. Ellis, Esq., in Vols. iv. and v. of this Journal 



Cuvier, llecherches sur les Reptiles douteux, in Humboldt's and Bonpland*s 

 Recueil d'Observations, &c — Mimoires du Museum d'Hist Nat., tome xiv. 



1827. Sur le Genre de Batraciens nomme Amphiume Philosoph. Trans. 



by Shreibers and John Hunter.— Wilson's Illustrations of Zoology. 



