HEREDITY AND VARIATION 221 



cestors have done. But again ex hypothesi its 

 original ancestor was unicellular all its life. 

 How did the first multicellular form arise ? 

 Certainly not by memory. 



Last of all there is the chemical theory of 

 inheritance which seems as if it was going to 

 be the popular theory of the immediate future. 

 It is not necessary to deal with this at any 

 great length for, in the first place, the argu- 

 ment which has just been used as to arrange- 

 ment will and must apply here also, and 

 secondly because the extreme rigidity of chemi- 

 cal and physical processes here affords a proof 

 that though they go on of course in living 

 things, they cannot be the dominant factors. 

 The ordinary reader can scarcely have any idea 

 ot the extreme rigidity and regularity of physico- 

 chemical phenomena. Let us take one example. 



The composition of stars distant billions of 

 miles from this earth and from one another is 

 ascertainable by spectroscopic examination, chemical 

 The variation in the spectra of different sub- rigidity 

 stances is due to the variation in the number 

 of vibrations per second of the electrically 

 charged systems of atoms. The number of 

 these vibrations is enormous, from 670 billions 

 per second at the violet end to 460 billions at 

 the red. Yet the vibrations are all perfectly 

 in time, for there is no blurring of the spectrum. 



