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THE AMERICAN NATURALIST [Vol. XL VI 



Plate) follow neither the Mendelian law nor the prin- 

 ciple of blended inheritance. 



On the unit-character doctrine we know that one of 

 three things is happening in the germ plasm. 



First, a " determiner ' ' may drop ont and we see a race 

 of mammals springing up without tails, or color, or hair. 

 In cattle the determiner for horns is dominant, therefore 

 something is added. 



Second, a "determiner" may be suddenly lost or modi- 

 fied, and we see excessive hair, curly hair, silky hair, 

 dwarfed or short limbs, brachydactylism. 



Third, and even more inexplicable, there occurs the 

 appearance of a new " determiner" or the removal of an 

 "inhibitor" and we observe horns suddenly arising on 

 hornless races like horses and rabbits. 



That fancy breeds can be established through the ab- 

 normal behavior and selection of these "determiners" 

 there is no question. That nature works through the 

 sudden appearance of new and favorable "determiners" 

 is as yet unproved; it is absolutely disproved in the case 

 of horns, for through paleontology we know that horns 

 arise in a continuous manner. The only mammal known 

 to us at present in which it would appear that a duplicate 

 horn may have sprung into existence through saltation 

 is Tetraceros, the four-horned antelope of India. Salta- 

 tion is possibly of significance in the case of the sudden 

 alteration of hair character because we know of a very 

 considerable number of curly-haired horses in Mexico 

 and South America, which are, however, eliminated by 

 breeders for the reason that correlated with curliness of 

 the hair are apt to arise certain other characters in the 

 hoofs and limbs which are unfavorable. 



Under wild or natural conditions in mammals we have 

 as yet secured no direct evidence of such origins or estab- 

 lishment of saltations either major or minor. There is 

 reason to believe that peculiar or anomalous mammals if 

 they do arise are driven away from the herds. 



It would appear that the obvious abnormality of the 



