Correlation and Application of Statistics to Problems of Heredity 61 



Galton in his Chapter III deals with the theory of Organic Stability, 

 illustrating it hy the model of a polygonal slab, which has positions of stable 

 equilibrium with various degrees of stability, i.e. which may require large or 

 only small displacements to pass from one position of equilibrium to a second. 

 He considers that his model (see Fig. 12) shows how the following conditions 



may co-exist: (l) Variability within narrow limits without prejudice to the 

 purity of the breed (i); (2) Partly stable sub-types (ii); (3) Tendency, when 

 much disturbed, to revert from a sub-type to an earlier form; (4) Occasional 

 sports which may give rise to new types (iii) (pp. 27-30). Again the whole 

 argument is one of analogy, and the reader may be pardoned a little vexation 

 when he finds such important topics as the Stability of Sports and Infertility 

 of Mixed Types only discussed (pp. 30-32) by reference to the analogy of 

 hansom cabs and the impossibility of their useful blend with four-wheelers*! 

 The fact, I think, is that Galton's own ideas at this time were obscured 

 by his belief that the ancestors actually did contribute to the heritage ; he 

 regarded the incipient structure of the new being to be the result of a clash of 

 elements contributed from many ancestral sources, and the resulting building 

 up out of more or less opposing elements of a particulate individual inherit- 

 ance as the result of chancef . A further source of difficulty to Galton in his 

 intei-pretation of hereditary phenomena lay in his mistake as to the nature 

 of regression. This forced on him the conception of positions of stable equili- 

 brium, each with its own centre of regression, and led him to the view that 

 evolution must generally proceed by sports, and not by minute steps. It is 

 true that on p. 32 he draws a distinction between the two views that the steps 

 may be small and that they must be small, but as he has elsewhere applied his 

 view of regression to indicate that small steps cannot be the source of evolu- 

 tion, the distinction is not really much of a concession (see our pp. 31-2). 

 The following words of Galton deserve, however, to be quoted not only 



* I find my copy of the Natural Inheritance, read and annotated forty years ago, defaced by 

 many marginal notes expressing anger at Galton's analogies in this Chapter. But these notes 

 were written before I had read and grasped the value of much of the later work in the book. 



t Of course the Mendelian appeals to the same doctrine of chance to explain the variation 

 in the members of an individual brood or litter, but he does so on the basis of homogeneous 

 germ cells having a heterogeneous factor formula. I am inclined to believe that the germ cells of 

 the same individual are not always and absolutely homogeneous, at any rate in the higher 

 organisms, and that the clash of elements to be determined by chance need not lie in the 

 factors of the formulae of the gametes, but in the fertilising germ cells themselves. 



