250 CHARLES R. STOCKARD AND A. L. JOHNSON 



The indices and proportions in table 2 are not derived from 

 a large number of skulls and might readily be objected to 

 as not having a sufficient statistical basis. This, however, 

 is not the primary importance of the table. It is arranged 

 simply to present the average values for the several skull 

 features and show the tendency in the different hybrid 

 generations to incline toward one or the other parent type. 

 A discussion of the detailed figures in table 2 is unnecessary 

 for present purposes, since the expression of the skull features 

 in the hybrids may be more easily appreciated from a con- 

 sideration of the following charts. 



Text-figure 57 has been arranged to show the measurements 

 of three skull features in the Boston terrier-dachshund cross. 

 Each heavy vertical line represents the exact value of the 

 dimension concerned in one particular skull. 



The upper series in the figure represents the total skull 

 index which is calculated by multiplying the zygomatic width 

 by 100 and dividing this by the length of skull base. The 

 value of the indices is indicated by the figures at the left. 

 The four dachshund skulls have uniformly low indices, (i(i 

 to 67, while the four Boston terrier skulls are uniformly high, 

 100 to 107, these being as wide as or wider than they are 

 long. 



Three F, skulls fall between the two parent stocks for this 

 index, their values being from 77 to 7i>; the deviation from 

 the round head of the Boston terrier is about twice as great 

 as from the long dachshund typed skull. 



The skulls of eleven F 2 hybrids show a wide range of from 

 71 to DO for this skull index. The lowest F 2 index is 4 units 

 above the dachshund and the highest is 17 below the Boston 

 terrier. Five of the eleven F 2 skulls are shorter than the F,, 

 five are about equal in index, and one is decidedly longer. 

 In other words, the F 2 skulls tend to spread in two directions 

 for this index, approaching the values of both parent stocks; 

 but in the cases represented by the chart, they fall a little 

 short of complete arrival in either direction. This important 



