EGG PRODUCTION. 79 



4. The general result of the comparison of the daughters of 

 "200-egg" hens with other pullets not daughters of "200-egg" 

 hens but receiving the same treatment, feed and care through- 

 out is that the daughters of the "200-egg" hens do not show so 

 high an average egg production as the others. Furthermore, 

 the daughters of "200-egg" hens do not conform so closely to 

 type as do the birds which are not daughters of "200-egg" hens. 

 The significance of these results lies not in the absolute values 

 of the positive differences in the case of the means and of the 

 negative differences in the case of the coefficients of variability, 

 but rather in the fact that they show with the greatest clear- 

 ness, that daughters of "200-egg" hens on the one hand were 

 certainly not better egg producers than other pullets, and on the 

 other hand certainly did not conform closer to a type in egg 

 production than did other pullets. 



DISCUSSION OF RESULTS. 



It is proposed to defer to ailother time and place the detailed 

 discussion of the significance of the results of this investigation 

 in their bearing on the general problem of selection. It need 

 only be pointed out here that, so far as they go, the results of 

 the present work are in entire accord with what has been found 

 in all the extensive and thorough studies made in recent years 

 on the subject of the effect of selection in different organisms. 

 There is rapidly accumulating a mass of evidence that the chief 

 if not the entire function of selection in breeding is to isolate 

 pure strains from a mixed population. It is found in actual 

 experience impossible to bring about by selection improvement 

 beyond a point already existing in the pure (isolated) strain at 

 the beginning. This is the result of the long continued exten- 

 sive and brilliant work of Nilsson * in plant breeding in gen- 

 eral. It is the essential result of Johannsen's ** selection experi- 



*Cf. DeVries, H. Plant Breeding. Chicago (Open Court Publ. 

 Co.) 1907. Pp. xiii~|-36o. 



**Johannsen, W. Ueber Erblichkeit in Populationen und in reinen 

 Linien. Jena (Fischer) 1903. Pp. 68. 



t Jennings, H. S. Heredity, Variation and Evolution in Protozoa, 

 II. Heredity and Variation of Size and Form in Paramecium with 

 studies of Growth, Environmental Action and Selection. Proc. Amer. 

 Phil. Soc. Vol. xlvii, pp. 393-546. 1908. 



