120 MAINE AGRICULTURAL EXPERIMENT STATION. IQII. 



their own experience has shown to be at least practically inade- 

 quate to meet their needs. 



Not only was there no improvement in average flock produc- 

 tion following the method set forth in the preceding section, 

 but actually there was a slight decline in production during the 

 selection period. No particular importance, however, is, in the 

 writer's opinion, to be attached to this decline. It probably is 

 to be regarded as due to chance, i. e., to a number of accidental 

 causes operating together. (See p. 156 for further discussion 

 of this matter.) 



The results of this earlier work aroused a good deal of pro- 

 test and criticism on the part of ardent believers in the efficacy 

 of mass selection under all circumstances. Furthermore many 

 persons have offered tentative explanations as to why these ex- 

 periments in selecting for improved egg production resulted as 

 they did. Some of these suggested criticisms and explanations 

 have been published, but most of them have not, but instead 

 have been confined to verbal discussions among workers inter- 

 ested in the problems of breeding. 



No attempt has been made by the writer to answer criticisms 

 of this work.* The discussion which follows has no polemic 

 object. When, as in the present case, the point at issue is the 

 critical interpretation of admitted results which are (and must 

 be in nearly all cases) in some degree incomplete no amount o'f 

 argumentation as to wdiat "might" or "ought" to obtain, really 

 helps very much in getting at the true facts. The most useful 

 course would seem to be first to examine critically all possible 

 interpretations and then devise if possible ways of testing ex- 

 perimentally which, if any, of these interpretations are really 

 valid. With the presentation of the evidence so obtained the 

 scientific case must rest, it seems to me, until additional and 

 directly pertinent evidence can be brought forward. While the 

 search for data bearing critically on the interpretation of breed- 

 ing experiments on fecundity at this Station is by no means 

 completed, yet it seems desirable now that certain of the posi- 

 tive results of the later experiments are to be presented to con- 

 sider critically the possible interpretations of the earlier work, 

 and to bring forward some of the evidence which has led the 

 writer to the opinion which he holds. 



* With the exception of the paper numbered 9 on the list at the begin- 

 ning. That paper deals only with a few special points. 



