210 WHAT IS LIFE 



masses of population by imperceptible steps 

 guided by selection, is, as most of us now see, so 

 inapplicable to the facts, whether of variation 

 or of specificity, that we can only marvel both 

 at the want of penetration displayed by the ad- 

 vocates of such a proposition, and at the forensic 

 skill by which it was made to appear acceptable 

 even for a time. In place of this doctrine we 

 have little teaching of a positive kind to offer."^^ 

 It was the early assumption on inadequate evi- 

 dence that a series of characters was successively 

 evolved. Perplexing difficulty attends the later un- 

 certainty of interpretation regarding the successive 

 or simultaneous and independent evolution of such 

 characters. (According to Eduard Seler, of the 

 Zeitschrift fiir Ethnologie, the problem is receiving 

 much attention. Felix von Luschan,^^ and others 

 treat of it.) 



A very great difficulty which attends the current 

 theory of descent, a difficulty which is receiving wide 

 and growing recognition, is the vagueness and crude- 

 ness of the conceptions of the causes and factors of 

 heredity and variation which were current sixty 

 years ago, and for which the later literature of the 

 subject offers no satisfactory substitutes. For today, 



" Problems of Genetics, 14, 248. 

 ^^ ZusammenJidnge und Konvergenz. 



