22 CHARLES E. STOCKAED 



Other domestic animals, such as sheep and goats, do not 

 show such marked violations of their original type and size. 

 These may be less widely hybridized in their origins, coming 

 from a more closely related ancestry. However, there is 

 among sheep a sporadic tendency to give rise to strange 

 mutant types. The classical case of the ancon ram was, in 

 the light of present knowledge, very clearly an achondroplasic 

 mutant in sheep. Many years ago I reported ('07) the case 

 of legless lambs sired on two different occasions by the same 

 ram paired with related ewes. Amelia, or leglessness, is at 

 times associated in its occurrence with achondroplasic stocks. 

 We shall refer to a few such instances that have recently 

 occurred among achondroplasic dogs in our experiments. 

 Such freaks among sheep and goats are, however, extremely 

 rare. 



During recent years wild stocks of rabbits have been crossed 

 in numerous ways under domestic conditions. Some of these 

 stocks have lately been reported by Greene, Hu and Brown 

 ( '34) of the Rockefeller Institute to give rise to structural 

 distortions and deficiencies comparable in many ways with 

 those known for man and the dog, but as far as behavior 

 is concerned these animals are again poorly suited for con- 

 stitutional studies. One of the most important problems in 

 the ultimate aim of our present investigation relates to the 

 influences of constitutional differences upon behavioristic and 

 psychological patterns. Few lower animals are suitable ma- 

 terial for such research, and none is so favorable as the dog. 



Divergent forms among the vertebrate species. Strange 

 and divergent body forms are not alone confined to man and 

 the domestic mammals and birds, but very closely comparable 

 peculiarities in size and type are found among numerous 

 species in other classes of vertebrate animals. Tiny, almost 

 microscopic varieties occur among the bony fishes, and there 

 may be reasons for considering these as truly midget types 

 or mutants from a much larger ancestral stem form. On 

 the other hand, there are gigantic species of fish with body 



