HEREDITY AND EVOLUTION. 5*9 



facts by an observer thoroughly conversant with the particular plant 

 or animal, its habits and properties, checked by the test of crucial ex- 

 periment, can disentangle the truth. 



To prove the reality of selection as a factor in evolution is, as I 

 have said, a work of supererogation. With more profit may experi- 

 ments be employed in defining the limits of what selection can accom- 

 plish. For whenever we can advance no further by selection, we strike 

 that hard outline fixed by the natural properties of organisms. We 

 come upon these limits in various unexpected places, and to the nat- 

 uralist ignorant of breeding nothing can be more surprising or in- 

 structive. 



Whatever be the mode of origin of new types, no theoretical evo- 

 lutionist doubts that selection will enable him to fix his character when 

 obtained. Let him put his faith into practise. Let him set about 

 breeding canaries to win in the class for Clear Yellow Norwich at the 

 Crystal Palace Show. Being a selectionist, his plan will be to pick 

 up winning yellow cocks and hens at shows and breed them together. 

 The results will be disappointing. Not getting what he wants, he 

 may buy still better clear yellows and work them in, and so on till his 

 funds are exhausted, but he will pretty certainly breed no winner, be 

 he never so skilful. For no selection of winning yellows will make 

 them into a breed. They must be formed afresh by various combina- 

 tions of colors appropriately crossed and worked up. Though breeders 

 differ as to the system of combinations to be followed, all would agree 

 that selection of birds representing the winning type was a sure way 

 to fail. The same is true for nearly all canary colors except in lizards, 

 and, I believe, for some pigeon and poultry colors also. 



Let this scientific fancier now go to the Palace Poultry Show and 

 buy the winning brown leghorn cock and hen, breed from them, and 

 send up the result of such a mating year after year. His chance of a 

 winner is not quite, but almost nil. For in its wisdom the fancy has 

 chosen one type for the cock and another for the hen. They belong 

 to distinct strains. The hen corresponding to the winning cock is 

 too bright, and the cock corresponding to the winning hen is too dull 

 for the judge's taste. The same is the case in nearly every breed 

 where the sex-colors differ markedly. Earely winners of both sexes 

 have come in one strain — a phenomenon I can not now discuss — but 

 the contrary is the rule. Does any one suppose that this system of 

 ' double mating ' would be followed, with all the cost and trouble it 

 involves, if selection could compress the two strains into one? Yet 

 current theory makes demands on selection to which this is nothing. 



The tyro has confidence in the power of selection to fix type, but 

 he never stops to consider what fixation precisely means. Yet a simple 

 experiment will tell him. He may go to a great show and claim the 



vol. lxv. — 34. 



