IMPROVEMENT OP WHEAT BY SELECTION 85 



fat parents, and some from parents only accidentally 

 fat. This is the general fate of mass selection. Some 

 improvement is made, but it is an improvement of 

 the average not of the whole, and progress towards 

 improvement is slow and tedious. Now, suppose the 

 sheep breeder recognized the difficulties of his task, and 

 instead of mixing up all the selected breeding sheep and 

 looking at the average of the resultant lambs, that he 

 mated the sheep separately and kept their offspring 

 separately under observation while giving them the same 

 feed. He would still get fat lambs and lean ones, but 

 he would be able to pick the parents that had produced 

 the fattest lambs, and know that these parents were 

 congenitally fat because they had transmitted the 

 character. Thus he would be able to pick out an early fat- 

 tening strain in a single generation, and would have only 

 to multiply that strain. The whole of the resulting flock 

 would then be early fatteners. This is the homologue 

 of "single ear selection." The problem above supposed 

 confronts the animal breeder only when he is buying 

 breeding stock and does not know how the animals have 

 been fed, never when he is selecting from his own stock 

 for breeding. But the problem confronts the plant 

 breeder in every first selection he makes. He can never 

 know if the apparent excellence of a head of wheat is an 

 inherent character or due only to an extra favourable 

 position in the soil, relative to manure, moisture, space, 

 etc. If all the heads are threshed together the resultant 

 offspring is a mixture of good and bad as the parents 

 were, and although repeated re-selection is bound to 

 produce improvement, the process is tedious and slow. If, 

 however, each head is threshed separately, and its seed 

 sown separately under similar conditions under strict 

 control, then the head whose progeny yields well will be 

 a congenitally good head, and that whose progeny is 

 indifferent will be an indifferent head, and look good only 



