BIONOMICS 271 



physiological and pathological development and to read all 

 biological antagonism in the light of values as one might have 

 wished him to do, yet his quasi bio-dynamic views again dis- 

 close his great grasp of biological principles. The unlikeness 

 among progenitors to him is only one antecedent of variation, 

 but by no means the sole antecedent. 



Were it so, the young ones successively born to the same parents 

 would be alike. If any peculiarity in a new organism were a direct 

 resultant of the structural differences between the two organisms which 

 produced it, then all subsequent new organisms produced by these two 

 would show the same peculiarity. But we know that the successive 

 offspring have different peculiarities ; no two of them are ever exactly 

 alike. 



One cause of such structural variation in progeny is functional 

 variation in parents. Proof of this is given by the fact that, among 

 the progeny of the same parents there is more difference between those 

 begotten under different constitutional states than between those begotten 

 under the same constitutional state. It is notorious that twins are 

 more nearly alike than children born in succession. The functional 

 conditions of the parents being the same for twins, but not the same 

 for their brothers and sisters (all other antecedents being constant) ; we 

 have no choice but to admit that variations in the functional conditions 

 of the parents are the antecedents of those greater unlikenesses which 

 their brothers and sisters exhibit. 



Variations in the functional conditions of the parents 

 are indeed answerable for much unlikeness of progeny. 

 This is strikingly manifested when the variations in bio- 

 economic functions in the long life of species are duly 

 accounted for. The majority of variational and specific 

 unlikenesses will then be seen to be but variations from one 

 great biological, viz., a symbiogenetic, theme. The testimony 

 from all sides in favour of this view is so overwhelming 

 that, in spite of the apparent fixity of "characters" and 

 their frequent segregations according to Mendelian ratios, we 

 have no choice but to admit that in the last analysis in Nature 

 it is bio-economic factors that are responsible for the arrival 

 and fate of noteworthy variations a recognition which, I 

 believe, has not its equal in importance in the whole field of 

 Biology. 



