ORGANIC POLARITY AND MUTATION 99 



matter to undergo isomeric changes (such as Spencer freely admits 

 and Weismann denies), coupled with Spencer's doctrines of 

 ' organic polarity ' and ' physiological units.' 



The sentence quoted from Herbert Spencer near the commence- 

 ment of this chapter shows plainly enough what he wished us to 

 understand by ' organic polarity.' If the molecules of alum during 

 the process of crystallisation had, under altered conditions, under- 

 gone some isomeric change, they would no longer have been able 

 to group themselves into the old form of the octahedron ; a new 

 mode of equilibrium among their molecules would have resulted in 

 a new crystalUne form and other new properties, as in other cases 

 previously quoted (pp. 44-47). But, as applied to lowest forms 

 of living matter, the doctrine of 'physiological units' and of 

 ' organic polarity ' means surely that the forms of low organisms 

 may be direct results of the attempts to establish a moving equi- 

 librium of the particular units entering into their composition. 

 As with the crystals, let us suppose that, under the influence of 

 some new conditions, isomeric .changes have been induced in the 

 molecular constitution of the pre-existing physiological units of 

 some simple organism, this should in accordance with Spencer's 

 doctrine result in the appearance of a new organic form in some 

 brief period and not, as he strangely enough suggests, in the 

 passage previously quoted, gradually and during a succession of 

 generations, extending over " an enormous period of time." 



This latter cannot be the legitimate interpretation of his doctrine, 

 as he himself shows in a later page (p. 705) when he says in refer- 

 ence to his hypothesis of physiological units : — " In its complete 

 form then the conception is that these specific molecules, having 

 the immense complexity above described, and having correspond- 

 ently complex polarities which cannot be mutually balanced by any 

 simple form of aggregation, have, for the form of aggregation in 

 which all their forces are equilibriated, the structure of the adult 

 organism to which they belong ; and that they are compelled to 

 fall into this structure by the co-operation of the environing forces 

 acting on them, and the forces they exercise on one another — the 

 environing forces being the source of the power which effects the 

 re-arrangement, and the polarities of the molecules determining 

 the direction into which that power is turned." 



Here then is one of the Factors of Evolution, of which no 

 account is taken by Prof. Weismann, but which my observations 

 on Heterogenesis compel me to regard as the all-powerful cause of 



