Influence of the Nervous System 675 
them was the newly regenerated nerve cord. Here also after 
thirty-two days, or more than sufficient time for regeneration to 
have taken place, only the cord had regenerated, but not quite to 
the amputated level, and the absence of the cord from the end 1s 
again associated with the absence of the new tail. 
No. 16.8. Removed the cord from the last 4 mm., no regenera- 
tion after 45 days. 
There was far greater injury to the bones of the vertebrze and to 
the muscles than in the preceding. The centra and hamal 
arches were almost completely destroyed. ‘The cord, like the pre- 
ceding, had regenerated, but only to within 2 mm. of the end. 
The far greater injuries to surrounding tissues may account for this 
retardation. However this may be, the absence of the cord is 
again associated with the failure to regenerate the tail. 
No. 16.9. Destroyed the cord from the last 4 mm., no regenera- 
tion after 61 days. 
Degeneration of the fibrous layer has proceeded farther cepha- 
lad than in any of the preceding animals, extending from about 
4mm. to the 7th mm. ‘The new cord has grown as far as the 
amputated end. Near the 4 mm. level, the inner lining of the arch 
has proliferated much cartilage. Distally however the neural 
arch, the centra and the hzmal arches were largely destroyed, leav- 
ing mere fragments of bone. These have proliferated cartilage 
that cemented many of the pieces together. Near the tip of the 
tail practically the entire skeletal structure was missing. 
More than twice as much time has elapsed than is ordinarily 
required for the new tail to appear. During this interval the new 
nerve cord has actually reached the amputated end. 
No. 16.10. Operation and time the same as the preceding. 
Like it, the fibrous layer of the cord had degenerated about 2 mm. 
cephalad. The very attenuated new cord had grown to and 
slightly beyond the cut end, into the cap of embryonic tissue. 
Like the preceding, the skeletal axis is practically gone from the 
end. ‘Tail had not regenerated. 
No. 16.2. The cord was destroyed from the last 34 mm. 
Regenerated a bud almost 1 mm. ‘Time, 92 days. 
Degeneration of the fibrous layer of the cord has proceeded over 
