12K) 



/iinio;/)/ ill Aiiirrica 



j)le filed by Darwin. Si ill other iiislaiiees are tiiose of liorn- 

 less eatlle, hairless clogs, l)oi)-tailecl cats, web-footed chiekens 

 and extfa-finjrered men. These however are exceptional 

 cases; the <i:reat mass of mntations, tliose mainly productive 

 of evolution, are of the minor sort, appreciable only by care- 

 ful measurement and statistical analysis. 



The presentation of the mutation theory in its present form 

 we owe nuiinly to tiie Dutch botanist, DeVries. A brief 

 resume of the hitter's work will bring the subject fairly be- 



iN 1 example of mu 

 Poulry, " Carncyie Instil u1 ion, PuliKcation 



A RuMPLESs Fowl 

 ton. J''roiii l)a\ i'n|iort, 



No. 



Inherit a nt-e 



in 



fore us. Over thirty years ago DeVries found certain well- 

 marked varieties of the evening primrose, a native of Amer- 

 ica, which had been introduced into Pairope and was grow- 

 ing as a weed around the city of Amsterdam. Specimens of 

 these varieties and of the parent species were transplanted 

 in his garden and bred for many years including eight gen- 

 erations, during wdiich time he discovered and recorded over 

 800 variations from the parent type, whose possessors bred 

 true to themselves. By selection of these variations he was 

 able to produce a large number of distinct types of prim- 

 rose which he called "elementary species," 



