312 CHARLES E. STOCKARD AND A. L. JOHXSOX 



that for the foregoing indices, and for this reason the basset- 

 hound long skull type is represented by high indices and 

 the short bulldog skull by low. The contrast between the 

 two types is, of course, shown with equal clearness by calcu- 

 lating the proportion of length to width or by doing the 

 reverse. 



The Fj skulls again approach close to the bassethound values 

 for this proportion of nasal length to palatal width. The 

 value of the F 2 skulls ranges almost down to that of the 

 bulldog skulls and completely as high as the lowest basset- 

 hound value. The majority of F 2 indices lie within the range 

 of the F x values. 



The two skulls from the backcross on the bassethound show 

 upper facial index values on a level with the highest pure 

 bassethound indices. This index for the backcross between 

 the F x and the bulldog sinks completely down to the lowest 

 levels of value for the poorest or least modified pure bulldog 

 skulls. 



The upper facial index is of definite significance for dif- 

 ferentiating between the normal long bassethound skull and 

 degrees in tendency toward the deformed short bulldog skull. 

 In crosses between the bassethound and the bulldog, the ele- 

 ments concerned in the calculation of the upper facial index 

 are dependent upon a genetic complex of factors; some of 

 these factors are dominant in the direction of normal ex- 

 pression while others are recessive for normal growth when 

 in contact with those factors which influence the modifications 

 toward the bulldog skull. Such an interpretation is indicated 

 by the range shown for this index in the twenty-one F 2 hybrid 

 skulls. The inclination of the pattern of the backcross hybrid 

 skulls in the direction of the parent stock on which the back- 

 cross is made also indicates the complexity of the characters 

 from which this index is calculated. 



The lower chart in text-figure 68 represents the values of 

 the breadth-height index. This index, based on the relation 

 between the distance from the auditory meatus to bregma 



