GENETIC TYPE AND THE ENDOCPJNES 307 



The two backcross bassethound skulls have skull indices 

 of 65, which is close to that of the pure bassethound, while 

 the two backcross bulldog skulls likewise approach the pure 

 bulldog with indices of 90 and 95. The higher of the latter 

 two backcross skull indices is still 20 units below the two 

 highest indices of the eight bulldog skulls, although it is only 

 1 unit under the lowest. Such relations would indicate that 

 most of the factors influencing those characters which de- 

 termine this index are dominant for the bassethound long- 

 skull, while a few factors for the short and wide growth of 

 the bulldog head tend to dominate sufficiently to modify the 

 long normal condition. The short achondroplasia skull of 

 the bulldog by no means bears the same simple genetic relation 

 to the normal long skull as was found for the short achondro- 

 plasic legs of the bassethound when contrasted genetically 

 with the normal long legs of the shepherd dog. Achondro- 

 plasic shortness of the extremities is inherited as a single 

 gene dominant, while the achondroplasia short head results 

 from a complex of genie influences of which most, but not 

 all, are recessive to the genes for normal. 



The chart for snout index (maxillary canine width in 

 proportion to snout length) is given in text-figure 66. These 

 indices show greater differences between the bulldog and 

 bassethound skulls than any other proportional dimensions 

 recorded. The six bassethound skulls have snout indices of 

 58, 58, 65, 66, 69 and 71. The same indices for the ten 

 bulldog skulls range from 139 up to 200, or from about 

 two to almost three times higher than the bassethound in- 

 dices. This contrast is due to the fact that the bassethound 

 skull has the common long protruding upper jaw or muzzle 

 of the ordinary dog while the upper jaw of the bulldog is 

 short and wide ; in poor typed bulldog skulls it is only about 

 two-thirds as long as wide, and in high typed skulls about 

 half as long as wide. The range for this index among the 

 six bassethound skulls is only 13 units, as against 61, almost 

 five times more, among the ten bulldog skulls. 



