APPENDIX I. 



Weismann's Law of Heredity, 1885. — This is based 

 upon the almost absolute distinction in every plant and 

 animal between the physical body or soma and the germ- 

 ceU, male or female, which the soma encloses, and which, 

 when fertilised, becomes the germ of a new individual. 

 The essential part of the theory is that the environment 

 does not directly influence the germ-ceUs but only the 

 soma, and that none of the characters acquired by the 

 soma during its life-time alters the essential constitution 

 of the germ-ceU and is transmitted through it to the next 

 generation. The germ- cell is therefore sacrosanct and 

 race is everything; training and environment may im- 

 prove or debase the individual but not the stock. This 

 theory is directly opposed to the old conception of 

 heredity, enunciated by Lamarck in 1809, according to 

 which acquired characters may be transmitted as such 

 from generation to generation. Though Weismann may 

 have pushed his arguments too far, yet his theory in its 

 broad bearings appears to be true and it has certainly 

 stimulated subsequent research along healthy and fertile 

 lines. 



APPENDIX II. 



The Mendelian Theory, 1865, 1901.— This theory of 

 transmission fits in weU with the Mutation or Saltation 

 theory of variation and Weismann's theory of heredity. 

 Gregor Mendel (1822-1884), the son of a peasant in 

 Austrian Silesia, was a priest and afterwards abbot of an 

 Augustine monastery in Briinn, Moravia, and his great 

 discoveries in heredity form one of the most romantic 

 chapters in modern science. His researches on pea- 

 hybrids were published in 1865 in an obscure local period- 

 ical. They were neglected by the learned in his life- 

 time and for many years passed out of knowledge until 



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