106 CHARLES R. STOCKARD 



ward rotation of the carpal bones in the wrist joint, and 

 under this condition the pressure of the body weight directing 

 the leg bones medially rotates the unobstructed carpals and 

 abducts the front foot in a manner characteristic of achondro- 

 plasia, with the wrists knocked in close together (see the 

 front views of animals in plates 11, 12, 16, 17, 18, and 19). 

 This modification of the extremity, as we have shown in the 

 foregoing genetic experiments, arises through the influence 

 of a single dominant gene which in the homozygous state 

 accentuates the expression. 



Figure 2 in plate 23 shows the right foreleg skeletons from 

 Fj hybrids between the bassethound and the three other pure 

 breeds from which the leg skeletons in figure 1 were taken. 

 The F x skeletons are arranged in an order comparable to 

 the pure group, that is, the bassethound-Saluki at the left, 

 the bassethound-shepherd next, and the bassethound-bulldog 

 last. Just as in the pure breeds the Saluki bone is longest 

 and slenderest, so in the F x hybrids the bassethound-Saluki 

 leg skeleton is longest, least modified, and slenderest. 



The scapula in each of the F t skeletons is much broader 

 than that of the long legged parent and approaches the high 

 index of the bassethound parent. The humerus in the three 

 F 1 legs is longest, and least bent and twisted in the basset- 

 hound-Saluki (left) ; shorter and more bent and twisted in 

 the bassethound-shepherd (center) ; and shortest, most de- 

 cidedly bent and twisted in the bassethound-bulldog (right), 

 as the photographs very clearly illustrate. The radius and 

 ulna are progressively more modified in length and form as 

 we compare the skeletons from the bassethound-Saluki 

 through the bassethound-shepherd to the bassethound-bulldog. 

 The radius and ulna of the F x bassethound-Saluki are not 

 badly bent nor twisted when compared with the normal long- 

 leg, but they are much shorter and thicker than in the leg of 

 the pure Saluki. The distal condyle of the ulna in the F, 

 bassethound-Saluki extends about as far below the distal 

 articular surface of the radius as in the case of the foreleg 

 of the pure bulldog shown in the parent group. Lateral out- 



