BLOOD AND VITELLINE VESSELS IN AMPHIBIA 367 
the body-wall that the lateral cutaneous vein is shut off from view. 
Indications of other perpendicular vessels begin to show them- 
selves in the lower extension of the body-wall, and soon, in a similar 
manner, a second series of perpendicular branches and a second 
parallel is developed (figs. 18, 29). I have no clear indication 
that this second set is formed from the vitelline vein at an early 
stage before circulation in the new vessels is perfectly established, 
as it is difficult to make out all of the vessel ends before there is 
blood in them. Usually there are from eight to eleven perpendic- 
ulars in this second set, but their number and distribution, like 
those of the first, are somewhat variable. This second body-wall 
parallel may be interrupted in its course, some times in its central 
part, or near the head or tail end, and not always symmetrically 
on the two sides. The blood runs from the head region towards 
the tail in the cephalic part of the system and from the tail region 
cephalad in the caudal segments. Although I could not trace it 
very clearly, I am sure that the first and second parallel and per- 
pendicular sets of somatic vessels change somewhat by the time 
the next series is developed. 
- At about 14 mm. length (figs. 19, 30, 31 and 32) a third, more 
ventral, somatic parallel is formed, while by this time the first is 
more or less covered by pigment. This third, in some specimens 
at least, seemed rather smaller than the others and with only a few 
communications with the lateral. Parts may not all be connected 
with each other and the current of the blood is from the cephalic 
region. ‘There are at first however, only a few cephalic connec- 
tions. The vitelline veins, which have been large up to this time, 
are now reduced to one main ventral trunk with fewer and less 
marked branches. It seems that some of the functions of the 
visceral circulation were taken over by the progressively greater 
growth of the somatic system. The body-wall is now well down 
on the reduced yolk sac. 
In larvae of 20 mm. (figs. 20 and 33), taken with the female 
although well able to swim, there is some indication in the yellow 
yolk sac on part of the intestine that the yolk is not yet all absorb- 
ed. The vessel from this and from the intestine is now clearly 
a part of the portal vein and the body-wall is completed below it. 
