298 CHARLES R. STOCKARD AND A. L. JOHNSON 



seven and six F x hybrids were obtained, a total of twenty- 

 three individuals. Seven of these F x females were paired 

 with various F x males to give twenty-three litters of F 2 

 pups. These F litters ranged in size from only a single 

 puppy to a litter of ten, and the twenty-three whelpings gave 

 a total of 150 F 2 hybrids. Three backcross matings between 

 the F! and the bassethound were made, producing litters of 

 seven, six and nine, a total of twenty-two backcross basset- 

 hounds. The reverse backcross by the Fj with the bulldog- 

 gave four litters, containing three, five, seven and six puppies, 

 a total of twenty-one backcross bulldog hybrids. In all, 216 

 hybrid animals from various combinations between the basset- 

 hound and bulldog were produced in our kennels. These 

 hybrids were studied during life for growth and behavior; 

 and after death their endocrine glands and various other 

 tissues were studied both in the gross state and microscopi- 

 cally. From these various studies we hoped to approach an 

 understanding of the interrelations among the endocrine 

 modifications and the genetic constituents in determining 

 the morphologic types of animals. 



THE HEAD AND SKULL FEATURES IN ENGLISH BULLDOG- 



BASSETHOUND HYBRIDS; NEW TYPES FROM NEW 



CONSTITUTIONAL COMPLEXES 



From the previous chapters of this study we are familiar 

 with the highly altered achondroplasic skull and head of 

 the English bulldog. We have also seen the normally well 

 developed quality of the bassethound skull and head as shown 

 by the indices and measurements in table 1 (p. 208). It is to 

 be recalled that both these pure breeds are of ordinary size 

 with neither dwarf nor giant growth tendencies. Photographs 

 of highly typed specimens of the bulldog and bassethound 

 breeds, along with their F t hybrids and a litter of four F 2 

 animals, may be seen by again referring to plate 19 (p. 97). 

 Skeletons of the same groups are photographed in plates 20 

 and 21 (pp. 99 and 100). 



