TRANSPLANTATION OF LIMBS IN AMBLYSTOMA 129 
for differences in the number of spinal segments which contrib- 
ute nerves to the limbs in different species, but it would also 
account for slight variations in the segmental contribution to 
the limb plexus in a given species—a condition which, as has 
been referred to above, has long since been observed. 
If the extent of the limb rudiment were the only factor to 
account for this latter phenomenon, then the limb rudiment, if 
displaced the distance of several segments, should so effect the 
nerve contribution that the new plexus would come from seg- 
ments corresponding to the position occupied by the displaced 
limb rudiment. The results of the experiments reported in this 
paper indicate that, in addition to the position and extent of the 
limb rudiment, still other factors govern the innervation of 
limbs when developed from rudiments lying beyond the con- 
fines of the orthotopic position. 
Fig. 5 Camera-lucida drawing of an embryo of Amblystoma in the tail-bud 
stage. The circle situated ventral to the pronephros (pn) indicates the position 
of the limb rudiment. X 15. 
EXPERIMENTAL 
The experiments were carried out upon embryos in the tail- 
bud stage (fig. 3). The extent of the limb rudiment at this 
period has been described above. The technique employed in 
embryonic limb transplantation is so well known through the 
papers of Harrison, Braus, and others that no special description 
is here required. All of the experiments were made upon the 
anterior limb rudiment. The majority consisted of transplant- 
ing the right anterior limb rudiment to an abnormal (hetero- 
topic) position on the same side of the body from which it was 
, 
