68 
JANE I. KOJBEUTSON. 
wardly directed current (PL 5, figs. 1, 3 and 4, Sp. V. L). 
Again at the distal end of the bulbus the anterior termination 
of the aortic septum does not taper off imperceptibly into the 
dorsal wall^ but presents a solid vertical surface that would 
offer some resistance to regurgitation from the two anterior 
pairs of aortic arches (PL 5, figs. 2 and 4, S. Ao.). 
It is of interest to note that the grooves formed between 
parts (1) and (2) and parts (2) and (3) of the bulbus are 
respectively homologous with the proximal and distal ^^Knick- 
ungsfurche’^ described by Grreil in the developing bulbus 
cordis of Lacerta (9). 
B. Arteries. 
In the adult four afferent vessels arise in two sets of two in 
close proximity on either side, from the very short ventral 
aorta at the anterior end of the bulbus cordis (PL 5, fig. 1, 
A, A.). 
Dorsally four efferent vessels join on either side to form the 
dorsal aortic roots, and these again, by their junction in 
the middle line, form the dorsal aorta (Text-fig. 2 Ao.) ; 
the two posterior pairs of afferent vessels arise somewliat 
from the dorsal surface of the ventral aorta, while the two 
anterior pairs are placed more ventrally. The proximal part 
of the anterior vessel on either side is really the paired ventral 
aorta, which, after passing a short distance outwards and 
forwards in the floor of the mouth, is prolonged into the 
lingual artery (Text-fig. 2, L. A.) anteriorly, immediately 
posterior and external to which it gives off the third aortic 
arch (the most anterior of the persisting aortic arches). In 
the adult this aortic arch (Text-fig. 2, A. A. 3) curves outwards 
dorsally and backwards and then inwards to the outer margin 
of the roof of the mouth, where it joins the dorsal aortic root 
at the point of origin of the dorsal carotid artery (Text-fig. 
2, Car.). The dorsal root then passes inwards and slightly 
backwards, and is joined in rapid succession, a short distance 
from the middle line, first by the fourth, and then by the short 
