48o THE GRAMMAR OF SCIENCE 



a really considerable amount of quantitative measurements 

 of heredity has already been collected, — such values seem 

 to fit the observed facts fairly well in the case of blended 

 inheritance. In other words, we have a certain amount of 

 evidence in favour of the conclusion : TJiat ivJieneve7' the 

 sexes are eguipotent, blend their characters and mate pangavi- 

 ously, all cJiaracters will be inherited at the same rate. Such 

 a result could hardly be attained if evolution had itself 

 produced heredity. It suggests that heredity, like varia- 

 tion, is something fundamental to the vital unit, and is 

 not a product of evolution itself^ Environment, largely 

 influencing organs and characters, may fictitiously reduce 

 or increase heredity, if the offspring be not reared in the 

 same environment as their parents ; homogamy and other 

 forms of sexual selection sensibly alter the pangamic values 

 of the correlation coefficients ; but these modifications 

 of heredity are only apparent, and provide no ground 

 for the assertion that heredity is the product of evolution 

 itself (see p. 475). 



It will be of interest to the reader to see the theo- 

 retical strength of collateral inheritance. This is given 

 for 7 = I in the accompanying table, where some of the 

 relationships are stated in male terms, but equally well 

 apply to females. A considerable increase may be 

 obtained on these values if 7 be taken greater than unity. 

 Thus for 7 = 2.35, the relationship between brothers is 

 expressed by .6596 instead of .4000. Whether such an 

 increase is really necessary, further observations and 

 measurements alone will show. At present ,4 seems to 

 agree fairly well with the results for pangamic mating. 



The reader will understand now my remarks on p. 429, 

 that assortative mating in man makes husband and wife 

 for eye-colour more alike than first cousins. They are for 

 stature more alike than uncle and niece. 



Another interesting deduction from the law of ancestral 

 heredity is the solution it appears to provide for the 



1 There is nothing more remarkable in heredity and variation being in- 

 herent in vital units, than in the same mother-liquid crystallising out into 

 crystals of approximately the same shape. 



