GENETIC TYPE AND THE ENDOCRINES 491 



of ancestral characteristics which are in many cases incon- 

 gruous and disharmonious in function. The majority of the 

 viable members of the second hybrid generation are unstable 

 and defective in behavior. 



In the third place, it should be emphasized that on hybridiz- 

 ing mammals with contrasted features and characters, many 

 of which are influenced in both their development and func- 

 tion by the state of their endocrinic balance, we are dealing 

 with a far more complex genetic and developmental inter- 

 action than exists among lower invertebrate forms without 

 specific endocrinic systems. The consequences of hybridiza- 

 tion on human races and stocks can only be fully understood 

 by experimental studies on higher mammalian forms in which 

 the genetics of endocrinic differences and influences must fol- 

 low paths closely similar to those in human beings. The 

 study of the endocrines from the Boston terrier-dachshund 

 generations definitely shows that the glands of the F 2 hybrids 

 vary considerably. In size they range not only above and 

 below the two parent stocks but far above the increased size 

 in the F, animals. The histologic qualities of these F 2 endo- 

 crines are often more distorted and pathologic than those 

 of either ancestral stock. 



None of the results from the Boston terrier-dachshund 

 cross offer encouragement to the indifferent attitude fre- 

 quently expressed towards crossing and hybridizing the 

 various human stocks. The attitude towards hybridizing the 

 domestic breeds of animals is considerably more cautious, 

 due, of course, to the serious economic consequences that 

 would result from careless breeding. 



FURTHER TESTS ON THE SIGNIFICANCE OF ENDOCRINIC 



QUALITY IN RELATION TO PHYSICAL TYPE AS 



SUPPLIED BY BASSETHOUND-BULLDOG HYBRIDS 



The results from only one cross between contrasted types 



would hardly be sufficient to indicate whether comparable 



disturbances might be expected among the hybrid progeny 



from other combinations, and for this reason these experi- 



