676 A. Ff. Goldfarb 
34 mm. Near theend of the old cord the fibers have disintegrated 
completely. The new cord extends almost to the tip of the tail. 
The neural arch had been injured but only slightly, resulting in the 
characteristic proliferation of cartilage inside the arch near its 
distal end. The end bud gives the impression that a new tail was 
about to develop. 
The next seven animals were chosen from a very much larger 
number which, though operated in the same manner as the preced- 
ing, nevertheless grew new tails, in some cases as large and com- 
plete as the control animals. 
No. 16.14. Tail amputated about the middle. Three milli- 
meters of the cord destroyed. Sixty days later the new tail had 
regenerated 44 mm. long. 
Actually 22 mm. of the cord was destroyed, thereby destroying 
the cord cells from the distal two pairs of spinal nerves ‘This 
would not be enough to prevent some motor innervations to the 
cut surface. Subsequently the cord degenerated anteriorly about 
1? mm., which may have and probably did remove the source of all 
the motor stimuli to the end. Yet in this case and in those to 
follow a new tail appeared, provided the skeletal axis and nerve 
cord were present at the amputated level. ‘The nerve cord in the 
sections showed a gradual shrinkage posteriorly. “The vacuolated 
fibrous layer is succeeded by a layer of embryonic fibers. The 
neuroglia cells increase in numbers and migrate laterally in each 
vertebra, to form the two primitive dorsal ganglia, and posteriorly 
to constitute the regenerated cord, Fig. 7. No clear line separates 
the old from the new cords, yet they are quite different. ‘There 
were no medullated fibers in the regenerated tail. Concerning 
the musculature and skeleton we need not enter into details here. 
It may suffice to state that the old muscles give rise to the new, 
that the old bony vertebrz regenerated the cartilaginous skeleton of 
the new tail, that the parts of the latter, growing at different rates, 
produce first the centra and then the simple bars that constitute 
the neural arch, and lastly the hzmal arch. 
No. 15.6 differs so little from the preceding that the account there 
given will substantially serve for this animal. 
No. 15.1. This animal regenerated a tail 5 mm. long. It differs 
from the preceding two animals as follows: (1) 44 mm. of the 
