1903.] 



AXATOMY OF THE JAPANESE SALAMANDER. 



309 



than the posterior end of the coiius arteriosus. It seemed to me 

 to pass from it to the surface of the auricle near to the opening 

 of the latter into the ventricle. 



In the heart of Menohranchtis, as Huxley has shown and as I 

 have observed myself, the synangium ends in a single (that is, of 

 course, apparently single) trunk, which leaves the pericardium in 

 the anterior middle line. In Megalobatrachits, on the other hand, 

 as I have already pointed out, the synangium gives rise to two 

 aortic trunks, which leave the pericardium separately one on each 

 side. There is not, however, by reason of this a vacant space left 

 between the anterior end of the synangium and the anterior wall 

 of the pericardium. On the contrary, a rounded piece of tissue 

 of a different colour and appearance to the synangium fastens it 

 to the anterior wall of the pericardium. This piece of tissue was 

 dissected, and the dissection reveals that the mass of tissue contains 

 a cavity, which runs for a very short way beneath the synangium. 

 Physiologically, I imagine this structure acts as a kind of buffer 

 to prevent impacts during contraction of the heart against the 

 anterior wall of the pericardium, and the fact that the " buffer " 

 is holloAv would aid its efficiency in that capacity. 



Text-fig. 32. 



Junction of vascular arches of Megalobatrachits to form dorsal aorta. 



A, vertebral arterj' ; Ao, dorsal aorta ; B, carotid arch ; h, deep carotid ; 

 C, fii'st aortic arch ; c, muscular branch ; D, second aortic arch. 



The Dorsal Aorta is formed by the union of three of the 

 " branchial " arches. Hyrtl, however, figures * only two of these 

 ai-ches as taking part in its formation, viz. the second and third. 

 I shall presently deal more minutely with the course and branches 

 of the various arteries which issue from the synangium. But the 

 broad outlines of their course will be apparent from the drawing 



* ioc. cit. pi. xi. lig. 4.' i. 



