No. 642] VARIATION IN REPRODUCTION 



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to the cause of variation lias perhaps resulted. Can we 

 not, it is asked, by subjecting the heriMliiaiy material to 

 chemicals, to physical agents, alter it, as we eaii alter 

 practically everything else in nature ? Of eoiii se we ran ; 

 it is easy. But when we alter it we usually kill it. or ])re- 

 v^ent it from developing; our task is like that eoiismnnia- 

 tion devoutly to be wished, of killing the ])atliogeiiie bac- 

 teria in a man— which is easy— but it also kills the man! 

 Have we succeeded in so altering the germ plasm, without 

 killing it, that it now develops differently, and transmits 

 the diversity to its progeny? 



It is easy by altering the chemical and physical condi- 

 tions to change tremendously the devel(>])inent and char- 

 acteristics of these creatures, and that without st()i)ping 

 life and reproduction. But in the infinitely greater pro- 

 portion of cases such changes have no inherited effect; 

 so soon as these particular conditions are removed, the 

 progeny go back at once to the usual constitution. Such 

 has been the result of extensive experiments of my own hi 

 modifying Parmnecium with chemicals; and of Xoyes in 

 modifying Kotifera. Startling transfoi-mations of form, 

 structure and function are readily produced and kept up 

 f..r o-enerations. hut .lisapMuar when the otrsi)rinu- are 

 reaiv.l under normal conditions. Onee in our work the 

 task >eeine(l accomplished. After many uvnerations of 

 treatment with alcohol. Pa ni nn.lu lu yiehh-d monstros- 

 ities and defoi-mities, analogous to those Stoekard ob- 

 tained by the same method in guinea pigs, and these de- 

 formities were transmitted after removal from alcohol, 

 for generation after generation. This was stirring; all 

 the energy of the laboratory was devoted to following the 

 monstrous stock through long periods, leaving the formu- 

 lation of pedigrees till time ])ermitte(l P.ut when this 

 could be done it appeared that all these ahnormal indi- 

 viduals came from one single ancestoi-. out of the Imn- 

 dreds with which the experinn^nt began; the icst had all 

 returned at once to normal. AN'e km»w that such hei-edi- 

 tarily abnormal stocks occur at times in Patamecium, 



