GENETIC TYPE AND THE ENDOCKINES 75 



of seven, each containing only one female puppy, while the 

 sister, 508 9 , gave a litter of eight and a litter of six with 

 only one male pup each, and a litter of seven and a litter of 

 nine with only two males each. Other litters produced by both 

 mothers were more nearly divided for males and females. 



The F 2 generation showed most instructive conditions in 

 leg length and bone type. The bottom row of plate 10 illus- 

 trates a single litter of seven F 2 adult animals. Three of 

 these, 14415 (fig. 5), 14395 (fig. 8), and 1445$ (fig. 11) are 

 double short or ss for achondroplasia ; three, 14405 (fig. 6), 

 1442 $ (fig. 7), and 1443 $ (fig. 9) are intermediate or mixed, 

 si; and one animal, 1444 $ (fig. 10) shows very long, II, Saluki 

 legs. Thus in this litter appear the three expected kinds of 

 legs : the dominant pure short ss, mixed short si, and the 

 recessive pure long II. But an element which was not so no- 

 ticeable among the bassethound-shepherd F2 animals, although 

 it w r as present, is clearly presented in these. The Saluki typed 

 bone and the bassethound typed bone tend to segregate in a 

 rather definite manner, while at the same time the achon- 

 droplasic growth occurs with both bone types. This fact in- 

 troduces a second element in the determination of leg length 

 and pattern and the degree of achondroplasic reaction, and 

 because of this second element the three animals, figures 5, 

 8 and 11 in plate 10, although diagnosed as double short, ss, 

 are not all equally short. No. 1445 9 (fig. 11) is the tallest 

 and 1439 $ (fig. 8) the shortest of the three. These two animals 

 are better shown and less reduced in size in plate 11 (fig. 3, 

 right, and fig. 4). The shortest one, 14395 (fig. 4) is seen to 

 have a most pronounced achondroplasic distortion of the 

 stocky, bassethound-like front legs. The two factors, ss, for 

 short affecting this stocky bassethound bone produced a very 

 pronounced reaction. Conversely, the pure ss short condition 

 acting upon the slender Saluki typed bone in 1445 9 (right in 

 fig. 3), produced a less marked effect, and this dog shows 

 legs almost as long as the mixed si F x hybrids (figs. 1 and 2) 

 and with even slenderer bone. This animal appears to have 

 almost pure Saluki typed bone and the achondroplasic modi- 



