58 INHERITANCE OF CHARACTERISTICS IN DOMESTIC FOWL. 



the second, the DR's; and their frequency is equal. One will not fail to 

 note that we are not here dealing with a case of blending simply, and the 

 inheritance of the blend; such a view is negatived by the fact of the much 

 greater variability of DR X DR cross over the simple D X R cross of the first 

 generation. One may safely conclude, then, that, despite the apparent 

 blending of booting characters in the first generation of hybrids, true segre- 

 gation takes place. But this is always to be seen through the veil of im- 

 perfect dominance. 



A casual examination of table 38 would seem to show a correlation 

 between the grade of booting of the parents and that of the average of their 

 progeny. Thus, on the whole, the parental grades run high in the upper 

 part of the table and run low in the lower part. This relation would thus 

 seem to confirm Castle's conclusion for polydactylism in guinea-pigs that 

 there is an inheritance of the degree of a character. One consequence of 

 such an inheritance would be that it would be possible in a few generations 

 to increase or diminish the grade of a character and fix any required grade 

 in the germ-plasm. A more careful consideration of the facts of the case 

 shows that this relation has another interpretation. The grade of boot of 

 the different parents varies largely because their gametic constitution is 

 diverse. As table 39 shows, the parents of the upper part of table 38 are 

 chiefly extracted recessives, and consequently their booting and that of 

 their offspring are characterized by high grades. On the other hand, the 

 parents of the lower part of the table are heterozygous or extracted domi- 

 nants and, consequently, their grades and also those of their offspring 

 average low. On account of the lack of homogeneity of the families in table 



38, one can draw from it no proper conclusions as to relation between parental 

 and fihal grades. On the other hand, from a homogeneous table, hke table 



39, we can hope to reach a conclusion as to the existence of such a relation. 

 I have calculated, in the usual biometric fashion, the coefficient of corre- 

 lation between average parental and fihal grades, and found it to be 

 - 0.17 ± 0.13. This can only be interpreted to mean that in a homogeneous 

 assemblage of famiUes there is no correlation between the grade of booting 

 of parents and offspring. 



