CRITIQUE OF THE ROUX-WEISMANN THEORY 



407 



E. Critique of the Roux-Weismann Thkorv 



It is impossible not to admire the thorou<(hness, candour, and lo^^ical 

 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 forma/ solution 

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

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



A 



D 



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 «yght 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 e.xact equality. 



