202 THE GENESIS OF SPECIES. [CHAP. 



however, needless to multiply instances, which can easily 

 be produced in large numbers if required. 



Secondly, with regard to teratology, it is notorious that 

 similar abnormalities are often found to co- exist in both 

 the pelvic and thoracic limbs. 



M. Isidore Geoffroy St. Hilaire remarks, 1 " L'anomalie 

 se repete d'un membre thoracique au membra abdominal 

 du meme cote." And he afterwards quotes from "Weit- 

 brecht, 2 who had " observe dans un cas 1'absence simultanee 

 aux deux mains et aux deux pieds, de quelques doigts, de 

 quelques metacarpiens et metatarsiens, en fin de quelques 

 os du carpe et du tarse." 



Professor Burt G. Wilder, in his paper on extra digits, 3 

 has recorded no less than twenty-four cases where such 

 excess co-existed with regard to both little fingers ; also 

 one case in which the right little finger and little toe were 

 so affected ; six in which it was both the little fingers and 

 both the little toes ; and twenty- two other cases more or 

 less the same, but in which the details were not accurately 

 to be obtained. 



Mr. Darwin cites 4 a remarkable instance of what he is 

 inclined to regard as the development in the foot of birds 

 of a sort of representation of the wing-feathers of the 

 hand. He says : " In several distinct breeds of the 

 pigeon and fowl the legs and the two outer toes are 

 heavily feathered, so that, in the trumpeter pigeon, they 

 appear like little wings. In the feather-legged bantam, 



1 "Hist. Generale des Anomalies," t. i. p. 228. Bruxelles, 1837. 



2 Nov. Comment. Petrop. t. ix. p. 269. 



3 Read on June 2, 1868, before the Massachusetts Medical Society, 

 vol. ii. No. 3. 



4 "Animals and Plants under Domestication/' vol. ii. p. 322. 



