Variation and Sflcction ; a üeply. 2ß3 



is the evidence of its existence? Nothing is said about this matter sub- 

 sequent to the lit 11 paper. In the present paper tiie authors are follow- 

 ing another clew. They adopt a gene hypothesis to account for the 

 quantitative variation exhibited by tlie eleven young and their descen- 

 dants. A purely statistical treatment of the series, that to the authors 

 reprehensible method, which "concerns itself exclusively with results 

 and absolutely neglects the causes of variation", would reveal no dis- 

 continuity here. It would arrange the animals in a series of stages of 

 increasiug blackness and would classify each animal in terms of these 

 definite quantitative stages. Such treatment would not preclude the 

 subsequent ai)piication to the series of any biological hypothesis one 

 chooses to test by it. But the Hageuoorns will have none of this. 

 Their vaunted analytical method begins with a preconceived idea. Tn 

 1911 it was "non-genetic factors"; today, when dealing with the same 

 series of observations, it is a gene, which they name K. This makes 

 the hooded rat blackei-. Hence the darkest hooded rats are supi)Osed 

 to be homozygous for this factor, the intermediate ones heterozygous, 

 and the lightest ones to lack it entirely. 



Fortunately for this theory, the "catastrophe" which brought 

 the Hagedooens rat colony to an end, made it impossible to test the 

 theory by breeding from the supposed homozygous recessives, the lightest 

 hooded individuals. To have obtained fr(Uii them as parents young 

 much darker than themselves would undoubtedly have given the theory 

 a jolt. For the authoi's state that on the gene hypothesis "selection 

 in the opposite direction will never succeed in bringing the lost genes 

 back, and therefore it would be impossible in an inbred family to bring 

 it [the minus selected race] back to its starting-point. Still, this would 

 be as easy, if selection in reality changed the germinal bases underlying 

 the character in question." My own extensive experience with reference 

 to this particular point shows that return selection from a minus selected 

 race is as easy as progress in the opposite direction. I therefore regret 

 that the Hagedoorxs were not able themselves to give this matter an 

 experimental test. 



We have in America a type of scientist who does things pait way, 

 but gives the impr'ession of full accomplishment. Oiu' of these climl)ed 

 part way up a mountain not previously ascended and subsequently 

 exhibited as evidence of his feat a photograph showing a view of the 

 plain below as seen from the mountain. It remained for a companion 

 later to disclose the fact that the picture was taken ])art way up the 

 mountain. The same man who climbed the mountaiu also sought the 



