50 GENETICS 



hairlessness in cattle, dogs, mice and horses, are fur- 

 ther instances of mutations. 



Davenport, 1 writing of his experiments with poultry, 

 says: "During the past four years I have handled 

 and described over 10,000 poultry of known ancestry. 

 Of striking new characters I have observed many, 

 some incompatible with normal existence; others in 

 no way unfitting the individual for continued life. 

 In the egg unhatched I have obtained Siamese twins, 

 pug jaws, and chicks with thigh bones absent. There 

 have been reared chicks with toes grown together by 

 a web, without toenails or with two toenails to a toe; 

 with five, six, seven, or three toes; with one wing or 

 both lacking; with two pairs of spurs; without oil- 

 gland or tail ; with neck devoid of feathers ; with cere- 

 bral hernia and a great crest; with feather shaft re- 

 curved, with barbs twisted and dichotomously branched 

 or lacking altogether. Of comb alone I have a score 

 of forms. All of these characters have been offered 

 to me without the least effort or conscious selection on 

 my part, and each appeared in the first generation as 

 well-developed peculiarities, and in so far as their 

 inheritance was witnessed, each refused to blend when 

 mated with a dissimilar form." 



Bateson (1894), in his "Materials for the Study of 

 Variation," gives a detailed list of 886 cases of "dis- 

 continuous variations" among animals, many of which 

 doubtless belong to the category of mutations, al- 



1 Davenport, C. B., 1909. "Inheritance of Characteristics in 

 Domestic Fowl." Carnegie Institution of Washington, Publica- 

 tion No. 131. 



