HEREDITY. 247 



portion to the whole skeleton, than do the same bones in the 

 wild duck ; and I presume that this change may be safely 

 attributed to the domestic duck flying much less, and walking 

 more, than its wild parent. The great and inherited develop- 

 ment of the udders in cows and goats in countries where they 

 are habitually milked^ in comparison with the state of these 

 organs in other countries, is another instance of the effect of 

 use. J^Tot a single domestic animal can be named which has 

 not in some country drooping ears ; and the view suggested by 

 some authors, that the drooping is due to the disuse of the 

 muscles of the ear, from the animals not being much alarmed 

 by danger, seems probable.'' Again — '^ The eyes of moles and 

 of some burrowing rodents are rudimentary in size, and in 

 3ome cases are quite covered up by skin and fur. This state 

 of the eyes is probably due to gradual reduction from disuse, 

 but aided perhaps by natural selection.'' * * * *^ It is well 

 known that several animals, belonging to the most differ- 

 ent classes, which inhabit the caves of Styria and of Kentucky, 

 are blind. In some of the crabs the footstalk of the eye re- 

 mains, though the eye is gone ; the stand for the telescope is 

 there, though the telescope with its glasses has been lost. As 

 it is difficult to imagine that eyes, though useless, could be in 

 any way injurious to animals living in darkness, I attribute 

 their loss wholly to disuse." The direct inheritance of an ac- 

 quired peculiarity is sometimes observable. Mr Lewes gives 

 a case. He '' had a puppy taken from its mother at six weeks 

 old, who, although never taught, 'to beg' (an accomplishment 

 his mother had been taught), spontaneously took to begging 

 for everything he wanted when about seven or eight months 

 old : he would beg for food, beg to be let out of the room, 

 and one day was found opposite a rabbit hutch begging for 

 rabbits." Instances are on record, too, of sporting dogs which 

 spontaneously adopted in the field, certain modes of behaviour 

 which their parents had learnt. 



But the best examples of inherited modifications produced 

 by modifications of function^ occur in the human race. To no 



