No. 606] 



METHOD OF GENETICIST 



363 



If YOU grant that evolution in the past was caiised by 

 the same agents as cause evolution to-day. to what ])he- 

 nomena of living things will you apply this i)iiiici])le? 

 Evolution requires two things, namely, modification and 

 inheritance. Given these two things, the occurrence of a 

 new characteristic and the inheritance (or even only the 

 heritahility) of the new characteristic, evolution has 

 occurred. It matters little now what becomes of the indi- 

 vidual or individuals possessing a new herital)le char- 

 acter. They may even perish before they leave offspring, 

 yet i'vohitioii lias occurred. What became of these 

 iiu'ipiciit l accs was the theme of the evolutionists of the 

 past hair century, who devised many and fanciful theories 

 to account for their preservation or their destruction. 

 To-day we are concerned less with the fitness of the new 

 characteristic for the environment; we demand rather to 

 know how the new feature arose and why it was inherited. 



Fortunately there is no fundamental disagreement with 

 regard to inheritance. Too nmch is known of the mechan- 

 ism of inheritance to allow of dispute. The chromosomes 

 have been saddled with tlio main ros])OTisi]nlitv. There 

 has lu.vcr been auv uciKM-al atf.-iP.pt to refer inheritance 

 to the environment. X<. inu. has >uiMH)>e.l that a -oose 

 egg laid ill tlie sand would jjroduce a turtle. It is true, 

 the cytojilasm has a share in determining what shall 

 develop from an egg; so does oxygen, and so do other 

 components of the medium, as can be readily shown by 

 altering those com])onents. What develops in the pres- 

 ence of tills cyto]t]a<ni. and ont of this cytoplasm, depends 

 si)eciticaliy. howevei'. upon the chromosomes. Disputes 

 regarding tlii- fact have seldom been dragged into argu- 

 ments over the method of evolution. 



W\{\\ the primary rei|iiirement of evolution, the pro- 

 duction of new chaiacter>, matters have been otherwise. 

 The mode of origin of modifications has not sliared the 

 good fortune of the mechanism of heredity. There is no 

 need to cite the hosts of opinions that have l>een lield l)y 

 reputable scientists regarding the inception of evolu- 



