INHERITANCE OE FECUNDITY IN DOMESTIC FOWE. 387 



It cannot justly be urged against the conclusions of this study 

 that the Mendelian hypothesis advanced to account for the 

 results is so complicated, and involves the assumption of so 

 many factors or such complex interactions and limitations of 

 factors, a to lose all significance. A? a matter of fact the whole 

 Mendelian interpretation here set forth is an extremely simple 

 one, involving essentially but two factors. This surely does not 

 indicate excessive complication. To speak in mathematical 

 terms, by way of illustration merely, it may fairly be said, that 

 the formula here used to 'fit' the data, has essentially the 

 character oi a true graduation formula, rather than that of 

 an interpolation formula. The number of constants fhere fac- 

 tors) in the formula is certainly much less than the number of 

 ordinates to be graduated. 



There is no assumption made in the present Mendelian inter- 

 pretation which has not been fully demonstrated by experi- 

 mental work to hold in other cases. That the expression of a 

 character may be caused by the coincident presence of two (or 

 more) separate factors, either of which alone is unable to bring 

 it about, has been shown for both plants^" and animals by a 

 whole series of studies in this field of biology during the last 

 decade. To find examples one has only to turn to the standard 

 hand-books summarizing Mendelian work, as for example those 

 of Bateson and Raur. Again sex-linkage or correlation of char- 

 acters in inheritance has been conclusively demonstrated for 

 several characters in fowls by the careful and thorough experi- 

 ments of a number of independent investigators. Finally it is 

 to be noted that Bateson and Punnett (4) have recently shown 

 that the inheritance of the peculiar pigmentation characterictic 

 of the silky fowl follows a scheme which in its essentials is very 

 similar to that here worked out for fecundity. 



The selcdion problem 



The results of the" present investigation have an interesting 

 and significant bearing on the earlier selection experiments on 

 fecundity at this Station. It is now quite plain that continued 

 selection of hiehlv fecund females alone could not even be ex- 



" Particularly important here are the brilliant researches of Nilsson- 

 Ehle (24, 25) on cereals, and of Baur (2) on Antirrhinum. 



