179 



Heredity. — Variability would not be of much use in. evolu- 

 tion where it not that physical characteristics can be trans- 

 mitted from parent to offspring. A tendency to variability 

 will exist in all organisms, although the amount of that 

 tendency will vary within very large limits. Heredity may 

 be either a help or a hindrance to evolution, as has been 

 plainly shown by Romanes. In the case of. the Australian 

 aborigines, which has it been? According to the "Law" of 

 Delboeuf, quoted by Romanes, a constant cause of variation, 

 however insignificant it may be, changes the uniformity of 

 type little by little, and diversifies it ad infinitum. From 

 the homogeneous, left to itself, only the homogeneous can 

 proceed ; but if there be a slight disturbance in the homo- 

 geneous, the homogeneity will be invaded at a single point, 

 differentiation will penetrate the whole, and, after a time — 

 it may bo an infinite time — the differentiation will have dis- 

 integrated it altogether. Has this differentiation which 

 existed amongst Australian aborigines been accentuated or 

 diffused by heredity ? Prof. Pearson and his colleagues, writ- 

 ing on "Genetic (Reproductive) Selection" in the Philosophi- 

 cal Transactions of the Royal Society of London, vol. 192, in 

 their concluding remarks, make the following statement : — 

 There is, so to speak, in every species an innate tendency to 

 progressive change, quantitatively measureable by determin- 

 ing the correlation co-efficients between fertility and organic 

 characteristics and between fertility in the parents and the 

 offspring. This "innate tendency" is no mysterious force 

 causing evolution to take place in a pre-ordained direction, 

 it is simply a part of the physical organization of the indivi- 

 dual which does not leave fertility independent of physique 

 and organic relationship, or leave these characters uncon- 

 trolled by the principle of heredity. The suspension of na- 

 tural selection does not denote either the regression of a 

 race to past types, as the supporters of panmixia suggest, 

 or the permanence of the existing type as others have be- 

 lieved. It really denotes full play to genetic or reproductive 

 selection, which will progressively develop the race in a man- 

 ner which can be quantitatively predicted when once we know 

 the numerical constants which define the characters of a 

 race and their relation to racial fertility. In other words, 

 natural selection must not be looked upon as moulding an 

 otherwise permanent or stable type; it is occupied with 

 checking, guiding, and otherwise controlling a progressive ten- 

 dency to change. 



Heredity, in the presence of free intercrossing, cancels the 

 tendency to variability, causing fixity of type. A considerar 



