CRITIQUE OF THE ROUX-WEISMANN THEORY 



407 



E. CRITIQUE OF THE ROUX-WEISMANN THEORY 



It is impossible not to admire the thoroughness, candour, and logical 

 skill with which Weismann has developed his theory, or to deny that, 

 in its final form, it does afford up to a certain point a formal solution 

 of the problems with which it deals. Its fundamental weakness is its 

 cal character, which, indeed, almost places it outside 



C D 



Fig. X 83. Half and whole cleavage in the eggs of sea-urchins. 



A. Normal sixteen-cell stage, showing the four micromeres above (from Driesch, after Selenka). 

 B. Half sixteen-cell stage developed from one blastomere of the two-cell stage after killing the other 

 by shaking (Driesch). C. Half blastula resulting, the dead blastomere at the right (Driesch). 

 D. Half-sized sixteen-cell stage of Toxopneustes, viewed from the micromere-pole (the eight lower 

 not shown). This embryo, developed from an isolated blastomere of the two-cell stage, segmented 

 like an entire normal ovum. 



the sphere of legitimate scientific hypothesis. Save in the maturation 

 of the germ-cells ("reducing divisions"), none of the visible phenom- 

 ena of cell-division give even a remote suggestion of qualitative divi- 

 sion. All the facts of ordinary mitosis, on the contrary, indicate that 

 the division of the chromatin is carried out with the most exact equality. 



