SPINAL CORD REGENERATION. I A77 
well codrdinated. Some, however, had difficulty in locomotion. 
All of these latter were deformed, the posterior end of the body - 
being bent ventrally on the anterior at the point of operation. 
The varying amounts of gaping of the wound appear to have 
little effect on the appearance or behavior of the animals as long 
as a considerable quantity of yolk is present. This provides a 
support for the body and preserves its normal form. The sup- 
port thus given is removed with the absorption of the yolk and 
bodily deformities, which were not previously noticeable, then 
come to light. Many of the slightly abnormal larvae subse- 
quently overcome this, but where the amount of bending exceeds 
a by no means definitely determinable maximum, the deformity 
increases with further growth. These embryos and tadpoles 
will be discussed in detail later. At the stage under consideration 
(4 days after operation) the amount of deformity exhibited by 
even the most abnormal larvae was slight. 
Sections of larvae killed at this stage show that the with- 
drawal of the skin from its earlier position between the surfaces 
of the cut has progressed so far that it no longer forms even a 
partial barrier to the regeneration of the cord (figs.4and 5). The 
mass of notochordal sheath tissue is still interposed between the 
cut ends of the spinal cord, but its fibers have become somewhat 
less closely packed about the periphery. 
Evidence is at hand that a further retraction of the ends of 
the cord from the site of the cut has occurred. With the ex- 
ception of the first and second pairs, the long axis of the spinal 
ganglia in this stage is normally directed ventrally and cau- 
dally. In these operated embryos, the first two pair of ganglia 
caudad to the cut (the 4th and 5th or 5th and 6th, as the case may 
be) have their long axes directed ventrad and cephalad. The 
sensory axones of the ganglion cells make their connections with 
the cord shortly after the 48 hour stage. The upper ends of the 
ganglia are thus attached: to the cord and the lower ends to the 
myotomes. With the increase in length of the embryo, accom- 
panied by the gradual retrogression of the cord ends from the cut, 
these ganglia have been pulled over to their new position. No 
such criterion of the shortening of the anterior end of the cord is 
