GENETIC TYPE AND THE ENDOCRINES 303 



type and features, the several Fj hybrids would individually 

 inherit very different complexes of the factors involved. 



The skull as a whole in the F : hybrids is shorter than in 

 the bassethound but the hybrid mandible is not equally 

 shortened. Among the twenty-three individuals of this gen- 

 eration, seventeen show prognathism of the mandible, or the 

 so-called undershot condition characteristic of the bulldog 

 skull. 



The average indices and proportions for the skulls of 

 thirty F 2 bassethound-bulldog hybrids are recorded in the 

 fourth column of table 4. These average indices are found 

 to be almost the same as those for the Fj hybrids. The 

 standard deviations in the F 2 group are, however, much 

 higher, being in the highest case thirteen times greater than 

 the standard deviation for the Fj group. Nevertheless, even 

 these differences in deviations do not convey an adequate 

 picture of the great variety of type modifications exhibited 

 among the F 2 hybrids as compared with the F! hybrids in 

 this cross. These facts we shall demonstrate in other ways. 

 The average indices in the fourth column of table 4 are still 

 important as showing that thirty F 2 skulls selected at random 

 may lend their features for an average amalgamation into 

 the indefinite F x type in spite of the highly pronounced and 

 divergent characteristics which exist among them. From the 

 biological standpoint, there can be, of course, no average for 

 these F 2 skulls, since the most significant thing about them 

 is the fact that they are so generally and widely different, 

 having been obtained from hybrids having new and unique 

 genetic complexes derived from the recombination of factors 

 from the widely contrasted parent stocks. The profitable study 

 of these hybrids in our present problems does not depend 

 so heavily upon large numbers and statistical methods, but 

 more directly upon a thorough analysis of the individual 

 differences in structural and functional features exhibited 

 among the members of each hybrid generation. 



