No. 602] 



THE SELECTION PROBLEM 



89 



the Illinois corn work, as Surface'^^ y^^y clearly demon- 

 strated. The writer<53 showed a number of years ago that 

 it was the basis of success in selecting poultry for egg 

 production. One strongly suspects it to be true in the 

 other cases, though because the importance of the point 

 has not been perceived, evidence in the published ac- 

 counts is lacking on which to make any positive statement. 



What is the correct interpretation of these favorable 

 results? Two opposed opinions are held. Fortunately 

 the heat of the controversy has been intense enough to 

 produce some distillation and we at least have the issue 

 very clearly and sharply defined. On the one hand it is 

 held, because there has been an alteration of type in point 

 of time coincident with successive selections, that sel- 

 tion on the basis of personal somatic qualities only, 

 such, in and of itself, has altered hereditary factors in the 

 germ plasm. This view makes selection a cause of genetic 

 variation,^* a total reversal of the position held by Dar- 

 win and most of his followers. The opposing view is that 

 selection can only be successful in altering the type when 

 hereditary determiners to produce the desired somatic 

 qualities are already present in the germ plasm. Selection, 

 on this view, has nothing whatever to do with the causa- 

 tion of the variation, and is wholly powerless and with- 

 out effect on the race unless either {a) the basis of the 

 selection is directly gametic, by means of progeny per- 

 formance test, or (&) the somatically selected individuals 

 happen by good fortune to carry the necessary hereditary 

 determiners in their germ plasm. 



The opposition here really goes ver\' far back. It is 

 the world-old fight between heredity and environment, 

 nature and nurture, germ and soma. One side believes 

 first, that hereditary determiners or factors fluctuate reg- 



«2 Surface, F. M., IV' Conf. internat. de G^n^tique, Paris, 1911, pp. 221- 

 235. 



«3 Pearl, E., Amer. Nat., Vol. XLV, pp. 321-345, 1911. 

 "Castle, W. E., Sci. Mo., Vol. 2, p. 91, 1916, and Castle, W. E., and Phil- 

 lips, J. C, Carnegie Inst. Publ. 195, p. 31. 



