388 MAINE AGRICUI.TURAI, EXPERIMENT STATION. I912. 



pected to produce a definite and steady increase in average flock 

 production. The gametic constitution of the male (in respect 

 especially to the L2 factor) plays so inmortant a part in deter- 

 mining the fecundity of the daughters that any scheme of se- 

 lection which left this out of account was really not 'systematic' 

 at all, but rather almost altogether haphazard. It has been re- 

 peatedly shown in the body of the paper that the same propor- 

 tion of daughters of high fecundity may be obtained from certain 

 mothers of low fecundity as can from those of high fecundity- 

 provided both sets of mothers are mated to males of the same 

 gametic constitution. What gain is to be expected to accrue 

 from selecting high laying mothers under such circumstances, at 

 least so far as concerns the daughters? 



'Selection' to the breeder means really a system of breeding 

 Xike produces like,' and 'breed the best to get the best ;' these 

 epitomize the selection doctrine of breeding. It is the simplest 

 system conceivable. But its success as a system depends upon 

 the existence of an equal simplicity of the phenomena of inherit- 

 ance. If the mating of two animals somatically a little larger 

 than the average always got offspring somatically a little larger 

 than the average, breeding would certainly offer the royal road 

 to riches. But if, as a matter of fact, as in the present case, a 

 character is not inherited in accordance with this beautiful and 

 childishly simple scheme, but instead is inherited in accordance 

 with an absolutely different plan, which is of such a nature- that 

 the application of the simple selection system of breeding could 

 not possibly have any direct effect, it would seem idle to con- 

 tinue to insist that the prolonged application of that system is 

 bound to result in improvement. 



It seems to me that it must be recognized frankly that wheth- 

 er or not continued selection of somatic variations can be expect- 

 ed to produce an eff'ect on the race depends entirely on the mode 

 of inheritance of the character selected. In other words, any 

 systematic plan for the improvement of a race by breeding must 

 be based and operated on a knowledge of the gametic condi- 

 tion and behavior of the character in which improvement is 

 sought rather than the somatic. Continued mass selection of 

 somatic variations as a system of breeding, in contrast to an in- 

 telligent plan based on a knowledge of the gametic basis of a 

 character and how it is inherited, seems to me to be very nidch 



