178 H. L. WIEMAN 



It is also to be noted in figure 16 that the original anterior 

 end of the transplant (to the right) is larger than the opposite 

 end, and that the axis of the brain stem (above) points toward 

 this larger end. Thus it would seem that the junction at this 

 point with the transplant was brought about by descending fibers 

 growing back from the brain not in a straight line, but toward 

 the original anterior end of the transplant. This same fact 

 appears from an examination of sagittal sections, where it may be 

 recalled that the connection between the anterior stump and the 

 transplant lies for the most part to one side of the midline, the 

 side nearer to the original anterior end of the transplant. 



Figure 16 also shows that the connection with the posterior 

 stump leaves the transplant from its posterior end (to the left), 

 which would be expected on the assumption that the transplant 

 had retained its original anteroposterior polarization. As a 

 result there is a zig-zag in the restored neural axis, which, evidence 

 from older stages (figs. 12 to 14) shows, may be later partially 

 straightened out. 



II 



The disturbance caused by the operation to which these 

 embryos were subjected must be profound, and it seems remark- 

 able that reestablishment of morphological and functional con- 

 tinuity to the extent noted occurs with such frequency in the 

 relatively small number of cases that I have studied. However, 

 the success of the operation depends to some extent upon the 

 region in which the transplantation is made. Thus in the experi- 

 ments considered up to this point the transplantations were made 

 in the region of the second to the fourth somites approximately. 

 Among these experiments only one case occurred from which 

 recovery seemed impossible or at least unlikely. 



Embryo T. L. 9, operated April 8th, showed by its reactions 

 to stimulation that connections through the transplant were 

 established by April 28th. At this time the embryo showed a 

 slight bend (ventral) in the body axis. As time went on, the 

 bend became more pronounced and response to stimuli more and 

 more sluggish, until by May 26th, when it was fixed, no evidence 



