THE BEGINNINGS OF LIFE. 587 



any internal tendency to vary, and explicitly states 1 

 that the environing forces are c the source of the power 

 which effects the rearrangement' under the influence of 

 changed conditions, and that the polarities of the mole- 

 cules simply determine c the direction in which that 

 power is turned.' Starting from his own c First Prin- 

 ciples ' it would seem that lower organisms must 

 possess an internal tendency to vary; whilst to attri- 

 bute so much influence to external rather than to 

 internal causes of change is about as convincing as 

 if Mr. Spencer were to assert that the heat which 

 ignites one extremity of a long train of gunpowder 

 is the cause of the effects produced, or c the source 

 of the power' unlocked, by the explosion along the 

 whole line 2 . 



Mr. Spencer has been led to adopt these doctrines, 

 apparently, in order to account for the fact of the 

 existence of multitudes of undifferentiated organisms 

 in the present day, and with the view of explaining the 

 apparent persistence of multitudes of other low types of 

 life through long geologic ages. As he did not believe, 

 when his c Principles of Biology' was written, that 

 any new evolution of living matter had taken place 

 within recent ages, multitudes of known facts must have 

 seemed quite irreconcilable with Mr. Spencer's general 



1 Appendix to ' Principles of Biology,' vol. ii. p. 488. 



2 Further arguments in support of the importance of internal ten- 

 dencies in producing an increasing complexity of organization are to be 

 found at pp. 123-129. 



