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 

 ^'//^j-z-metaphysical character, which, indeed, almost places it outside 



C D 



Fig. 183. — 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. 



