■No. 642] VARIATION IN REPRODUCTION 



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generation to generation, such as evolulitMi iiMiuiics, 

 should lie open before us, unconfusod. W'r >li<iul(l see 

 evolution occurring, as wo see water flowiiiu'. 



This ])l;iiiu simple and optimistic maxim has, T fear, 

 like many auotliei- such, not })rove(l so ilhiminating as its 

 promise. I5ut h'd by it, iiivestiuatoi's set tiiemselves at 

 the study of the passau'e of uvnerat ion-, with selection 

 and propagation of indi\idnals >lio\\ing (Ii^■ersities, in 

 these creatures wlieri' seemingl> all lastinu change from 

 parent to ()ffsi)ring nmst l)e evolutionary. Their hope 

 was to see evolution occurring. And what did they see? 

 I need not review the details ; dohannsen, I5ar])er, Hanel, 

 the present writer, Lashley, Agar, and others, followed 

 for long periods the passage of generations in many dif- 

 ferent org-anisms during uniparental reproduction. 



Their report, after years of work, was astonishingly 

 simple ami cleai-. As to the origin of hereditary varia- 

 tions, it i'e>rmbled the faiuous chapter on the Snakes of 

 Ireland. It summed itself, in effect, in the succinct, suffi- 

 cient, exhaust i\e pr.)posit ion that there is no inherited 

 variation: henee no ..rigin of su.-h variation. Tliere is 

 notliing to lind out about it. for it <l..esn't occur. The in- 

 dividuals produced in uniparental reproduction may in- 

 deed differ, luit tlu-e <liver>ities are transitory effects of 

 environnumal diffeivnco; they are n..t inherited. All 

 the doceiidant^ of a >iuule indi\ idual are genetically and 

 hereditarily alike: they form in effect a set of identical 

 twins. And from this it could In- conclmled that in bi- 

 ])arental i'e])i-oduction all \\w o])served <liversities are 

 due to the kaleidoscopic i-e,i;roui)ing of lu'n'ditary ma- 

 terials; nothing to e\'olutionary change. 



Outcries— objurgations and acclamation- L'ri'i'ted 

 these propositions. Some re\ihd them foi- tlu-ir maiu- 



trutii and the clarification they wrouglit. < ipixnu'nts 

 tried to dispr.)v<' them by inve>t i-al ing the matter them- 

 selves; their evidence strengthened the propositions they 



