SPINAL CORD REGENERATION. II 44] 
stage locomotion of the embryo as a whole will result from 
continued stimulation of the middle piece. The locomotion thus 
produced is in every way similar to that exhibited by those 
embryos in which the wounds have been primarily fused, but 
appears at a slightly later time. An explanation for the apparent 
delay in the appearance of the S reaction in the middle piece of 
those embryos in which the cord wounds were not permitted to 
fuse is not entirely clear, unless it be that the isolation of the 
middle segment from the head and tail and the consequent ab- 
sence of the support which a continuous skin over the embryo 
gives to it does not enable the myotomes to express their con- 
traction to as marked a degree. 
From this time on, the development of locomotion in response 
to stimulation proceeds slowly and is accompanied by the active 
regenerative processes which go forward in the embryo. Com- 
plete return to a normal condition of coordinated locomotion 
was seen only in two or three embryos in which practically com- 
plete reunion of the spinal cord had taken place. 
Spontaneous movement appears in the middle piece as soon as 
the double C reaction makes its appearance and is followed by 
voluntary movements of the head when it also passes into the 
double C phase. The tail is the last portion of the embryo to 
exhibit spontaneous movement. 
Correlation between the phase of reaction and stage of regenera- 
tion. From the work on embryos in which the spinal cord has 
been simply severed, it is apparent that the embryo is capable of 
performing swimming movements in response to stimulation 
before there is any nervous connection between the two ends of 
the cord and that a very simple type of voluntary swimming 
movement may arise before these connections have been estab- 
lished. It is further to be noted that apparently the only réle 
played by the nervous connections in the embryo is that of co- 
ordination in the later phases of the swimming movement. 
Exactly the same conditions are met with in all embryos in which 
a portion of the spinal cord has been reversed, whether the 
operation has been followed by the complete fusion of the 
wound surfaces or not. It has been noted in these experiments 
