BLOOD AND VITELLINE VESSELS IN AMPHIBIA ate 
an early stage of the ventral abdominal vein which seem to 
develop in connection with the cutaneous system (fig. 37). This 
ventral abdominal gives evidence of its paired origin even up to 
the adult. In early larval stages it lies in the ventral body-wall, 
but in later larvae it becomes somewhat separated from the soma- 
topleure. In sections, the cephalic portion of the vein is found 
to be very close to the vessels of the liver during an early period; 
later, this cephalic part of the ventral vein is found connected 
to the liver capillaries. Just when it first becomes united to 
liver vessels I was unable to determine, nor can I say anything now | 
of the possibility of its cephalic portion being developed from part 
of the vitelline system, but it develops in the somatopleure, while 
the vitelline is formed in the splanchnopleure. 
GENERAL CONCLUSIONS 
The blood develops from the mesoderm on the surface of the 
yolk. In Amblystoma it may be more clearly followed from 
ventral mesoderm and it develops more ventrally on the yolk. In 
Desmognathus its development does not begin from continuous 
thickenings of mesoderm but from isolated areas. 
The exact limits of axial and peristomial mesoderm are hard 
to determine, as Greil (’08) seems to recognize, so the conclusions 
of Mollier as to the early origin of the blood and the even earlier 
history of the blood- and vascular-forming cells given by Greil 
(08) must be considered to be somewhat theoretical. It is not 
difficult to duplicate in Amblystoma, the stages which these authors 
figure and describe, but it is much more difficult to do the same 
for Desmognathus. From the position of the blood islands in 
this species I cannot feel sure that some of the more dorsally 
placed blood masses are not from axial mesoderm. 
The reason why Desmognathus fusca forms blood islands as it 
does is probably due to the fact that the larger amount of yolk 
causes a more meroblastic type of development as is shown in its 
earlier stages. 
The development of blood from the surface of the yolk in the 
case of Bufo, as described by Mollier (’06), and its development in 
