380 The Outline of Science 



comes of a primary quality of living creatures, inherent in the 

 germ-cell the capacity of making experiments in self-ex- 

 pression. 



5 



As regards Heredity 



Darwin was one of the first to show that the mysterious 

 problems of heredity could be attacked scientifically, and his 

 cousin Sir Francis Galton went much further. But it is un- 

 fortunate that neither of them knew anything about the Abb6 

 Mendel, who published papers in 1865 which have revolutionised 

 the whole subject. His work remained practically unknown 

 till 1900. 



Mendelism 



There are three fundamental ideas in Mendelism. The 

 first is the idea of "unit-characters," and this requires a little 

 patience. By an inheritance is meant what the living creature 

 is or has to start with, when it is represented by a fertilised egg- 

 cell. Now it has been discovered that an inheritance is, in part, 

 built up of numerous, more or less clear-cut, crisply defined, non- 

 blending characters, which are continued in some of the descend- 

 ants as definite wholes, neither merging nor dividing. We may 

 think of the colour of the eye, the quality of the hair, the shape 

 of the nose. Strictly speaking, what lies in the inheritance is 

 not the character as seen in the adult but a germinal representa- 

 tive (technically called a "factor" or "gene") of the character. 

 The full-grown character, say the shape of the nose, is, as it 

 were, a product of the germinal representative and the surround- 

 ing influences which operate during development. It is also 

 necessary to understand that an adult character, like the quality 

 of the hair, may be represented in the germ-cell by several fac- 

 tors. Moreover, one germinal factor, e.g. the initiative for de- 

 veloping dark 'pigment, may influence several characters in the 

 adult. 



