XVI ARE ACQUIRED CHARACTERS INHERITED ? 321 



comfort, the turning serving to keep the rather stiff hair 

 all the right way, and also to brush away small hard 

 objects. Yet again, it is not alleged that all dogs do it, 

 and in many cases it may be a habit copied from the 

 mother. The uncertainties of the case are therefore too 

 great for it to afford an argument of any value. The 

 bower-bird's habits are more difficult to explain on any 

 theory, since the whole question of these alleged instincts 

 is unsettled. We have evidence that in many cases even 

 the peculiar song of birds is not instinctive in the species, 

 but is the result of imitation ; and Mr. Hudson has 

 recently shown that the fear of man in wild birds or its 

 absence, is probably the result of individual experience in 

 all cases. Till we know that the bower-birds' habit is 

 wholly due to inheritance and not to imitation of older 

 birds, we can hardly found any important conclusions 

 upon it. 



Horns and other Dermal Appendages. 



Many writers have laid stress on the difficulty of ac- 

 counting for the origination of new organs in certain 

 groups of animals, by variation and natural selection 

 alone. Horns are especially adduced ; and it is alleged 

 that there is no other way of explaining their origin 

 except by the habit of butting with the head, leading to 

 thickening of the skin and excrescences of the bone, 

 which, being transmitted by inheritance and increased by 

 use, gradually produce the various kinds of horns. In 

 like manner, the origin of flowers and their successive 

 modification, have been imputed to the irritation caused 

 by insects, leading to outgrowths which have been in- 

 herited and increased by further irritation. 



Taking the case of the horns, Mr. J. T. Cunningham, in 

 his introduction to the English translation of Eimer's 

 Organic Evolution, says : — '" No other mammals have ever 

 been stated to possess two little symmetrical excrescences 

 on their frontal bones as an occasional variation; what 

 then caused such excrescences to appear in the ancestors 

 of horned ruminants ? Butting with the forehead would 



VOL. I. Y 



