LIMITS OF DIVISIBILITY OF LIVING MATTER. 



63 



embryos resulted. The same fact can be shown by a method 

 that I published in "Oao. Journal of Morphology, 1892. If we bring 

 eggs immediately after they have been fertilized into sea-water 

 whose concentration has been sufficiently increased, the nucleus 



Fig. 4. 



Fig. s. 



Fig. 6. 



Fig. 7. 



begins to segment without any corresponding segmentation 

 of the protoplasm. If the eggs are then brought back into 

 normal sea-water, the protoplasm within from five to twenty 

 minutes divides into as many cleavage spheres as there are 

 preformed nuclei. This year I took up these investigations 

 again with Professor Norman with the same result. Professor 

 Norman found that the nucleus under such conditions con- 

 tinues to segment while the protoplasm does not divide, and 

 that in most cases the segmentation is certainly mitotic.^ 



1 T. H. Morgan reports in a note in the A)iatomischer Anzeiger that he has 

 repeated my experiments but obtained different results, namely, that the nucleus 

 does not segment in the concentrated solution, but like the protoplasm goes into 

 the resting stage. If Morgan had made more experiments, or if he had tried the 



