Benham. — Occurrence of Tiro Unusual Blood -vesarlx in Hyla aurea. 33 



or newt to whicli I have access {e.g., Bronn's Thierreich). In the sahi- 

 mander, as is well known, both the third and fourth arches persist, but 

 unite with the systemic to form the dorsal aorta. 



As I have noted, the third arch in the case under consideration is not 

 connected on either side to the dorsal aorta or with the systemic arch. 



2. Paired Lateral Abdominal Veins. 



A frog dissected by one of my students on the 4:th April rather worried 

 him because there was no " anterior abdominal vein," and so he called my 

 attention to it. I was surprised to find that in place of this median vein this 

 frog possessed a pair of laterally situated veins each of which, arising from 

 the femoral vein of its side and running forwards in the body- wall, quite 

 laterally entered the precaval (anterior vena cava) of its side. On its way 

 it received two musculo-cutaneous veins, which normally in this species enter 

 the anterior abdominal vein at the level of the tendinous intersections of the 

 rectus abdominis muscle. These lateral veins had no relation to the portal 

 system, but the vesicular vein from the urinary bladder passed forwards to 

 enter the hepatic portal at the spot at which the abdominal vein normally 

 does so. 



I can find no record of exactly this arrangement as occurring in the 

 frog, though cases of a right or left vein of somewhat similar relations 

 anteriorly have been described. 



BuUer* found an abdominal vein which after a normal course from the 

 hinder part of the body as far as the liver, to which it sent a smaU branch, 

 bent outwards to the right side and entered the right superior vena cava, 

 or, as the figure shows, the subclavian. 



The next case is that of Woodland,! where the abdominal vein is median 

 posteriorly but passes outwards to the left precaval (or subclavian). It 

 gives no branch to the liver. 



In the next year O'Donoghuef described a frog with an abnormal heart 

 and with an abdominal vein similar to that described by Woodland. 



These are the only instances of an abnormal condition of the abdominal 

 vein which I can find. In each of them the hinder end arises quite 

 normally from the union of the two femoro-abdominal or '' pelvic '" veins. 

 Each of these authors refers to the condition in Cemtodus, while Woodland 

 carries the comparison back to the paired lateral veins of the dogfish, which 

 homology was first suggested by Hochstetter in 1894. 



In the present case this resemblance is very evident and precise. Here, 

 too, is an instance of the persistence of a larval condition, though with 

 certain differences in detail. Marshall§ writes thus : " The anterior 

 abdominal vein is at first paired and is in connection not with the liver, but 

 with the heart. The pair of vessels appears first in the ventral body-waU, 

 extending backwards a short distance from the sinus venosus ; they soon 

 extend farther backward and acquire a communication with the veins of 

 the hind legs and of the bladder. At a later stage the two veins unite at 

 the hinder end in front of the bladder, while farther forward the vein of 

 the right side disappears and the left one alone persists ; later still the 



*A. H. R. Btjller, Journ. Anat. and Physiol., vol. 30, p. 211, 1896. 

 t W. Woodland, Zool. Anz., vol. 35, p. 626, 1910. 

 JC. H. O'DoNOGHUE, Zool. Anz., vol. 37, p. 35, 1911. 

 § Loc. cit., p. 184. 



2— Trans. 



