TRANSPLANTATION OF LIMBS IN AMBLYSTOMA 161 
nerves derived from segments of the cord posterior to the normal 
limb level, so that the restricted function which they do exhibit 
cannot be the result of a lack of peripheral innervation. It ap- 
pears, therefore, highly probable that the greatly impaired move- 
ments which these additional limbs exhibit are conditioned by 
a lack of supply of central efferent neurones. As has been 
stated above, there are probably a certain number of these de- 
scending neurones belonging to the tractus bulbospinalis which 
develop only as far as the normal limb level, where they discharge 
into the normal appendicular somatic centers. Assuming this 
to be true, the greatly restricted movements of the additional 
limb would readily meet an explanation on this basis; for, these 
descending neurones being taken up by the peripheral neurones 
of the normal limb, the movements of the additional limbs must 
very likely be effected through more or less imperfectly con- 
nected intraspinal, intersegmental correlation neurones of the 
levels from which peripheral innervation is derived. 
SUMMARY 
1. When the anterior limb of Amblysoma is excised and re- 
implanted to the same embryo at distances ranging from one to 
seven segments posterior to the normal position (autoplastic 
transplantations), there occurs a corresponding decrease in the 
function of such limbs as they are implanted more and more 
remote from the normal situation (table 1 a). 
2. Shifting the position of the limb a given number of body 
segments does not effect a corresponding shifting of the seg- 
mental nerve contribution to the plexus. There is a marked 
tendency for the transplanted limb to receive innervation from 
the normal limb level of the cord (table 2 and figures 10 and 11). 
3. Limbs removed so far posterior to the normal situation as 
to receive no innervation from the normal limb level of the cord 
received the main bulk of their nerve supply from segments sit- 
uated anterior to the transplanted limb rather than from seg- 
ments corresponding to the position occupied by the limb (table 
Dye 
