THE WONDER OF LIFE 517 



Unless, of course, selection is against them. In horticulture, 

 in particular, artificial selection has operated in great part 

 on mutations. If this interpretation be confirmed and 

 extended, it will not be necessary to lay such a heavy burden 

 on the shoulders of selection. But more facts are urgently 

 needed ; and how and under what conditions mutations — 

 whether adaptive or non-adaptive — occur, remains an 

 unsolved problem. 



(d) In his theory of Germinal Selection, Weismann has 

 elaborated an attractive subsidiary hypothesis. Supposing 

 that the germinal material consists of a complex — a multi- 

 pKcate — of organ- determining particles (the determinants), 

 he postulates a struggle going on within the arcana of the 

 germ-plasm. Supposing hmitations of nutrition within 

 the germ, he pictures an intra-germinal struggle in which 

 the weaker determinants corresponding to any given part 

 will get less food and will become weaker, while the stronger 

 determinants corresponding to the same part will feed 

 better and become stronger. While the external selection 

 of individuals goes on, and is all important, it is being 

 continually backed up by the germinal selection. Thus 

 nothing succeeds Hke success. 



(e) Various evolutionists — Profs. Mark Baldwin, H. F. 

 Osborn, and C. Lloyd Morgan — have suggested that al- 

 though individual adaptive modifications may not be 

 transmissible, they may have indirect importance in 

 evolution, by serving as Ufe-preserving screens until coin- 

 cident inborn or germinal variations in the same direction 

 have time to develop. As Groos expresses it, in reference 

 to some instinctive activities — Imitation may keep a 

 species afloat until Natural Selection can substitute the 

 life-boat heredity for the life-belt of tradition. 



