140 The Science of Life. 



Chapter XL 

 Heredity. 



A Modern Study The Facts of Inheritance Problems of Heredity 

 Theories as to the Uniqueness of the Germ-cells The Doctrine of 

 Germinal Continuity Elaborations of the Idea of Continuity 

 The Problem of Reconstruction Inheritance of Acquired Char- 

 acters Criticisms of Weismann's Position F'ilial Regression 

 Galtoris Law of Ancestral Inheritance. 



It must be admitted, even by the most pessimistic, 

 that the biologists of the Victorian era have made some 

 A Modem progress in the understanding of heredity, 

 study. or the relation between successive genera- 



tions. But if we measure what we can honestly say we 

 know in regard to heredity by what we should like to 

 know, we must confess that the serious study of the 

 subject has just begun. 



The great steps in the Darwinian era have been : (a) 

 the exposition of the doctrine of germinal continuity, 

 (b) a more precise investigation of the material basis of 

 inheritance, (c) the growth of scepticism as to the in- 

 heritance of acquired characters, and (d] the application 

 of statistical methods which have led to the formulation 

 of the law of ancestral heredity and the like. The most 

 important names are those of Weismann and Galton, 

 and the most fruitful methods have been (i) detailed 

 microscopic analysis as to the cellular phenomena of 

 reproduction, and (2) statistical researches as to the 

 facts of inheritance. What seems most needed at pre- 

 sent is a series of exact experimental studies in breeding, 

 continued through a series of generations. 



The general facts of Inheritance were first adequately 

 discussed in a classic work by Lucas (1847-1850). At 

 The facts of present they may be summarized as follows : 

 inheritance. ( T ) The general likeness between parent and 

 offspring is a commonplace of observation, condensed 

 in the familiar saying, " Like begets like". As varia- 

 tions which make the offspring different from the parent 



