Plate IX. 



Fig. 62. Transverse section through the injured region (mid-brain) of 

 the embryo shown in Fig. 63. Only the right neural fold is affected by the 

 operation, x 87.5. 



Fig. 63. This embryo shows the result of an operation made ten degrees 

 to the right of the median line, in the margin of the dorsal lip. The injury 

 was made thirty-four and three-fourth hours after fertilization, and then 

 incubated for thirty-six and three-fourth hours. X 20. 



Fig. 64. This shows the result of the operation for Experiment VII. The 

 injury was made thirty-six and three-fourth hours after fertilization, and 

 the egg was then incubated for thirty-six hours. The operation was made 

 just after the closing of the blastopore (see Fig. Y, K). X 21. 



Fig. 65. This shows the left side of a transverse section of an unincu- 

 bated hen's blastoderm. The figure is introduced to show the rounded con- 

 dition of the region of overgrowth, which is raised up from the yolk. I am 

 indebted to Professor George Lefevre for his generosity in sending me the 

 series from which this photogi'aph was made. X 128. 



Fig. 66. Posterior end of a median section from the blastoderm described 

 in connection with Experiment I (see text for description). X 120. 



Fig. 67. A portion of the same section taken just anterior to the pre- 

 ceding. X 120. 



