252 CHARLES R. STOCKARD AND A. L. JOHNSON 



These charts would suggest that the high and low skull 

 indices are truly hereditary features, although they are defi- 

 nitely not simple or single factor dominant or recessive 

 characters. The value of this index depends upon the influ- 

 ence of several genetic elements, and those tending to bring 

 about the low or long skull index are somewhat more dominant 

 in their influences than are the elements concerned in pro- 

 ducing the short Boston terrier skull. For this reason the 

 skull index in the Fj hybrid approaches more nearly that 

 of the dachshund. 



The middle chart in text-figure 57 represents the values 

 of the upper facial indices, nasal length to palatal width, 

 for the same skulls, arranged in the same sequence as for 

 the indices examined above. It will be recalled that the upper 

 facial index has been calculated in a manner the opposite 

 of that for the other indices, and thus the long skulls have 

 high rather than low values. 



The upper facial index in the four pure dachshund skulls 

 ranges from 92 to 100, in contrast with only 36 to 41 for the 

 four Boston terrier skulls. The FjS range from 62 to 70 and 

 again fall between the two parent types, being more nearly 

 midway between them for this index than for the total skull 

 index. 



The eleven F 2 skulls have a wide range for upper facial 

 index, from 57 to 78; five of these are below the F l range, 

 having a broader facial skeleton, and three have a higher 

 index than the FjS. The F 2 with the lo\vest index fails to 

 reach the Boston terrier index by 16 units and the F 2 with 

 the highest index falls short of that of the dachshund by 14 

 units. Thus the F 2 range fails to reach the parent indices 

 to about the same degree in both directions. 



The upper facial index in the backcross of the F! on the 

 Boston terrier ranges from 42 to 74. One of these skulls 

 approaches to within only one unit of the Boston terrier 

 index and thus is, for this feature, practically Boston terrier 

 in type. In spite of the fact that five out of the nine backcross 



