Plate III. 



' Fig. 22. Right half of a ti'aiisverse section tliroiigti tlie plane xx' of 

 Fig. XIII. X 259. 



Fig. 23. A portion of the right side of a section passing through wW of 

 Fig. XIII. X 259. 



Fig. 24. A portion of the central part of a section passing through vv' of 

 Fig. XIII. X 259. 



Fig. 25. A part of the region of overgrowth from the series which is 

 reconstructed in Fig. XI. It shows a large periblastic nucleus which has 

 moved down from the edge of the blastoderm. This is the only periblastic 

 nucleus in the series that was found either beneath or external to the 

 region of overgrowth, x ^57. 



Fig. 2G. Posterior portion of a median longitudinal section from a blas- 

 toderm taken thirty-seven hours after fertilization, or four hours before 

 laying. At "rf" is shown the dorsal-lip of the blastopore, which has been 

 enclosed within the zone of junction. It is doubtful whether the region 

 marked "gw'' should be regarded as germ-wall, x 152. 



Fig. 27. Left side of a median transverse section from a blastoderm taken 

 about thirty-five hours after fertilization, or six hours before laying. It 

 shows the beginning of the region of overgrowth at "o." x 138. 



Fig. 28. Posterior end of a longitudinal section from a blastoderm taken 

 four hours after incubation. Introduced to show the condition of the region 

 of overgi'owth at this time, x 138. 



