44 ALLEN 
VI. PERIPHERAL DISTRIBUTION OF THE ARTERIES. 
1. Branchial Arteries. 
As has already been stated in the paragraph on the general 
survey of the blood vessels, the aferent branchial arteries (Pls. 
I and II, figs. 1 and 12; A.Br.A.) are paired vessels, which 
convey the venous blood from the ventral aorta or branchial 
artery (Pls. I and II, figs. 1 and 12; V.Ao.) to the branchial 
filaments.. They arise as 3 paired trunks from the ventral 
aorta. The most cephalic pair supply the filaments of the first 
branchial arches; the second pair the filaments of the second 
branchial arches; and the third pair soon divide, the anterior 
forks supplying the third pair of branchial arches and the pos- 
terior forks, the last or fourth pair of branchial arches.” All of 
these vessels, which very closely resemble one another, run in 
the grooves of their respective arches and gradually exhaust 
themselves by giving off numerous afferent filament arteries 
throughout their entire dorsal course. 
The (Averent Brauthial Telament’ Vessels (Pl. 1, tig. 25 
A.Fil.A.) of 2 adjacent filaments arise as paired vessels, and 
running in a caudal direction along the inner or hypothenuse 
margins of their respective filaments, gradually exhaust them- 
selves in numerous afferent filament cross-vessels, which are 
only about 60 # apart. Proximally these vessels attain a con- 
siderable length, but gradually decrease in length distally. 
Each cross-vessel terminates in a dorsal and a ventral vessel, 
from which the filament capillary network (P\. I, fig. 2; Fil. 
Net.) arises. This network lies in a dorso-ventral plane in- 
1A gill or holobranch is composed of a double row of filaments or 2 hem?- 
branchs attached to the concave or posterior side of each branchial arch. These 
filaments have the form of right-angled triangles, attached by their short sides 
to the arches and the hypothenuse sides of each pair face one another. Each 
pair of filaments is not separated by a cartilaginous rod as is the case with the 
Elasmobranchs, but they usually overlap one another to some extent at their 
bases. 
? This appears to be the normal arrangement among the Teleosts; while in 
the skate one trunk may supply several branchial arches, and in the ratfish 
(Hydrolagus), I have observed that the ventral aorta gives off a pair of vessels 
for each pair of branchial arches. 
