TABLE OF CONTENTS 17 



PAGE 



between determinants. — Advantages of the new 

 hypothesis. — The idea of selection applied uni- 

 versally. — A discussion of germinal selection. — 

 A discussion of Weismann's system; the theory of 

 the germ plasm, the representation of characters, 

 the migration of biophors. 



CHAPTER XI 

 William Roux's Theory 163 



The organicist view and its distinctive characters. 



— Importance of external factors. — Exponents of 

 the theory: O. Hertwig, Herbst, J. Loeb, Driesch. 



— Tropisms and tactisms. — W. Roux and biome- 

 chanics. — The theory of " the mosaic "; the strug- 

 gle between parts of the organism ; functional stim- 

 ulation. — Evidence: the formation of spongy tissue 

 in bones, pseudarthrosis. — A discussion of Roux's 

 theory; its merits. — Its relation to selectionism 

 and Lamarckism. 



CHAPTER XII 



The Law of Galton and the Laws of Mendel . 176 



Heredity considered from a new point of view. 

 — Galton's statistical researches : the law of ances- 

 tral heredity. — Mendel's experiments. — The study 

 of hybrids; the law of dominance and the law of 

 segregation of characters. — Instances of the appli- 

 cation of these laws. — Theoretical consequences of 

 the Mendelian discoveries. 



