CASTLE. — LAWS OP HEREDITY. 227 



even to enable one to predict that result with any degree of accuracy, 

 and that too in the very category of cases which it was originally for- 

 mulated to cover, namely in color inheritance among mammals. Galton 

 himself ('97, p. 403) recognized the existence of such a defect, though he 

 considered it, for practical purposes, of little consequence. Stated in his 

 own words it is as follows : — 



"The chief line of descent," it is generally believed, "runs from germ 

 to germ and not from person to person." Yet " the person may be ac- 

 cepted on the whole as a fair representative of the germ, and, being so, 

 the statistical laws which apply to persons would apply to the germs 

 also, though with less precision in individual cases." Failure of Gal- 

 ton's law in the case of von Guaita's statistics is due to the falsity of the 

 assumption here made by Galton that the person is " a fair representative 

 of the germ." In all cases of alternative inheritance the person (or 

 soma) represents only a part of the ripe germs produced by the indi- 

 vidual, in some cases it may even represent none of them. Hence any 

 theory of heredity which bases its predictions as to the character of the 

 offspring solely upon the character of the soma of the ancestors, is clearly 

 inapplicable to cases of alternative inheritance. The presumption is 

 against its application to any other class of cases until that applicability 

 has been demonstrated. 



II. Mendel's Law of Heredity. 



Certain facts of alternative inheritance were clearly stated and ac- 

 counted for many years ago by Gregor Mendel ('66). He thus not only 

 formulated laws of alternative inheritance, whose correctness has been 

 fully confirmed by a number of independent observations, but he also laid 

 the foundation for a general theory of heredity. In the history of the 

 study of heredity his discovery is the most fundamental and far-reaching. 

 Its importance is not lessened by the fact that it was long unrecognized. 

 Only under the fertilizing influence of Weismann's ideas was the redis- 

 covery of Mendel's law accomplished independently by de Vries (:00), 

 Correns (:00), Tschermak (:00), and others. To its further develop- 

 ment no one has contributed more than Bateson (:02). 



Where Galton's law gives us at best rough approximations based 

 upon averages of heterogeneous material, and with no attempt at an 

 explanation of the results, Mendel's law enables us to make predictions 

 for specific cases as to both the character and the numerical proportions 

 of the offspring to be expected, and furnishes us at the same time with a 



