158 



Edzuin G. Conkhn. 



Development of Right Blastomere of 2-Cell Stage. 



Figs. 13-20. Successive stages in the development of the same right half embryo, the left blasto- 

 mere having been injured in the 2-cell stage; drawn at intervals of about five minutes. Here and 

 elsewhere the yellow protoplasm is indicated by coarse stipples. 



Fig. 13. Right half of 8-ceII stage, posterior view. A small amount of yellow protoplasm surrounds 

 the nucleus of the ectoderm cell b*--. The position of the cells shows that the ventral ends of the third 

 cleavage spindles diverged from the first cleavage plane in the posterior quadrant and converged toward 

 that plane in the anterior quadrant, just as in the normal egg. (See Conldin, ^05'.) 



Fig. 14. Right half of 1 6-celI stage, anterior view. The yellow crescent is seen through the cell B^- '. 

 In the normal egg of this stage the cells A"-' and a^»' lie more nearly in front of the cells A^-^ and a^-*. 



Fig. 15. Same stage as preceding posterior view. In normal eggs the cells B^-^ and b'^-'' lie nearly 

 behind the cells B^*' and b*-^ and not on their median side. 



Fig. 16. Right half of 30-cell stage, dorsal view. A'^-^ and A*-* are cells of the gray crescent; 

 B*»2 and B*-^, cells of the yellow crescent. 



Fig. 17. Right half of 34-cell stage, posterior view. In normal eggs the cell B"-* lies on the lateral 

 border of B^.^. 



Fig. 18. Same stage as preceding, dorsal view. The cell B''-' normally lies between B^-^ and A^'". 



