WHAT EVOLUTION IS 97 



preface in "Back to Methuselah," 

 who cry out for Lamarckism, but 

 their cry is far-fetched and aUhough 

 the Lamarckian doctrine may eventu- 

 ally prove true, the proof of it will 

 come from other sources than literary 

 intuition. 



The conclusion that Lamarckism is 

 a possible but unproved factor in evo- 

 lution is a statement that represents, 

 I believe, the opinion of the majority 

 of modern biologists. That the criti- 

 cism upon which this statement rests 

 applies to animals only in so far as 

 they exhibit sexual reproduction is, I 

 suspect, generally appreciated though 

 not so commonly stated. In organ- 

 isms that reproduce in this way, as 

 Weismann clearly showed, the cells 

 that make up the creature are divisi- 

 ble into the two classes of body cells 

 and reproductive cells and, as already 

 noted, it is extremely difficult, if not 



