GENETIC TYPE AND THE ENDOCRINES 253 



skulls closely approach the Boston terrier for this index, one 

 of those among the other four is further from the Boston 

 terrier than are the three FI skulls. 



The single backcross dachshund skull with an upper facial 

 index of 87 closely approaches this index in the pure dachs- 

 hund. 



From this chart it would appear that the upper facial 

 index, like the skull index, is definitely hereditary and also 

 depends upon the influences of more than one specific genetic 

 element for the complete expression of its type. The ex- 

 pression of an index might very well be of this nature, since 

 the factor or factors chiefly concerned in determining, for 

 instance, nasal length, may not be the same as those influ- 

 encing palatal width. Both these features are employed in 

 calculating the values for the upper facial index. 



The lower chart in text-figure 57 is arranged so that the 

 cranial indices of the several generations of skulls may be 

 compared. The differences in this index for the two pure 

 stocks are quite definite although not so large as the two 

 previous indices. The range for cranial index in the hybrid 

 generations is also more limited than those shown in the 

 above charts. In spite of these smaller differences, the cranial 

 indices still follow very clearly the trends which have been 

 pointed out for the two indices above. The Fj cranial index 

 lies between those of the parents. The indices among the 

 eleven F 2 s range completely down to those for the dachshund 

 skull and, in the other direction, fully up to those for the 

 Boston terrier skull. The backcross on the Boston terrier 

 gives skulls with very variable cranial indices ; although some 

 return to the Boston value, others fall as low as those of the 

 dachshund. All in all, this chart would seem to indicate in 

 definite fashion that cranial indices are of different values 

 in the dachshund and the Boston terrier skulls, even though 

 the values for the two breeds differ to only a slight degree. 



Text-figure 58 charts the very significant snout indices and 

 palatal indices for the same series of skulls represented 



