Influence of the Nervous System 691 
often badly injured or destroyed, as seen in Fig. 10. But this 
did not appear to have any effect on the regeneration of the tail. 
The other 14 animals examined differ in no radical respect from 
No. 17. They showed greater or less 1 injury to the surrounding 
tissues, or more or less extensive injuries to the cord, or spinal 
ganglia. Yet in no case could [ satisfy myself that the whole of 
the nerve cord had been removed from the entire tail stump, and 
that therefore the whole of the nerve innervation, either motor or 
sensory, had been removed. 
There can however be no question but that regeneration can 
take place when the greatest part of the cord and spinal ganglia are 
destroyed and inall probability after all the nerve influences have been 
removed. ‘The experiments furthermore corroborate Morgan and 
Davis’s conclusion that a new tail may be formed in the absence 
of the nerve cord from the amputated end. 
REGENERATION Of THE HEAD OF THE EARTHWORM (LUMBRICUS) 
IN THE ABSENCF OF A NERVE CORD AT THE CUT SURFACE 
The best example in support of the view that the presence of the 
nerve cord is the essential factor in regeneration, is that given by 
Morgan for the earthworm. Morgan (’02) removed the anterior 
segments of the earthworm and then cut out, fromthe ventral side 
of the amputated end, a narrow strip including skin, muscle layers 
and nerve cord. After a sufficient time had elapsed there appeared 
a new head, but only at the posterior end of the strip, 1. e., from the 
end containing the nerve cord. No head regenerated at the ampu- 
tated end, due, as Morgan believed, to the absence of the nerve 
cord. A modification of this experiment served to strengthen 
this conclusion. A similar strip or “window” was cut out, not 
from the amputated end, but beginning several segments posterior 
tothisend. As Morgan had anticipated two heads were produced, 
one at each anterior cut end, where the nerve cord was exposed. 
Joest and later Rabes were led to a similar conclusion as a 
result of their observations upon grafted worms. When the ven- 
tral nerve cords were free to come to the surface a head was regen- 
erated at that point. Nusbaum (’08) recently made some very 
