718 A. “f. Goldfarb 
After removal of nerve stimuli the regenerated organs may show 
certain malformations, but these are traceable to indirect effects 
of the operation upon nutrition, respiration, etc., of the tissues 
affected, or to mechanical stresses. ‘The primary fact of a normal 
regenerative process resulting in the development of all the parts 
typical of the missing organ is unquestioned. 
In the case of the tadpole, the evidence is not so conclusive. 
For, in order to prevent all nerve stimuli from reaching the ampu- 
tated end, it is necessary to destroy the nerve cord and the sensory 
ganglia from practically the whole of the tail. ‘This was difficult to 
do. I succeeded however in destroying the nerve cord in the tail 
except for isolated and very much injured fragments whose nerve 
connections appeared to have been completely broken. In this 
way all or very nearly all motor and sensory nerve stimuli were pre- 
vented from reaching the amputated end. A new tail however 
regenerated in every instance. ; 
The evidence is equally clear that even when motor and sensory 
stimuli reach the amputated region, regeneration cannot take 
place, if certain other organs are absent. For example, the forma- 
tion of a new tail in the frog tadpole may be completely prevented 
by removing the notochord from the cut end. The nerve stimuli 
from the intact nerve cord and sensory ganglia are not able to start 
the regenerative processes. In Diemyctylus also, development 
of a new tail can be prevented either by removing the skeletal axis 
of bone or cartilage, as in the tadpole, or by preventing the nerve 
cord from reaching the amputated surface. By the second 
method nerve stimuli are prevented from reaching the cut end 
by extracting a sufficiently long piece of the cord; or, by merely 
placing a very small plug at the end of the vertebral canal, the 
cord is prevented from reaching the amputated end without thereby 
interfering with the innervation. ‘Tails so treated did not regene- 
rate. In other words the absence of the skeletal axis or of the 
nerve cord from the end of the tail stops regeneration completely, 
although nerve stimuli were present. No one speaks of a “ mor- 
phogenic” influence exerted by the bone or cartilage. Have we 
any more reason for referring such an influence to the nerve cord? 
The ability of adult animals to regenerate in the total absence of 
innervation from the central nerve system is not limited to verte- 
