XIV FUNDAMENTAL PROBLESIS 417 



of the existence of .animals in a state of domestication, Ave 

 should expect to find that, in wild species, all unused parts or 

 organs had been reduced to the smallest rudiments, or had 

 wholly disappeared. Instead of this Ave find various grades 

 of reduction, indicating the probable result of several distinct 

 causes, sometimes acting separately, sometimes in combination, 

 such as those Ave have already pointed out. 



And if Ave find no positive evidence of disuse, acting by its 

 direct effect on the individual, being transmitted to the offspring, 

 still less can Ave find such evidence in the case of the use of 

 organs. For here the very fact of iise, in a Avild state, implies 

 utility, and utility is the constant subject for the action of 

 natural selection ; Avhile among domestic animals those parts 

 Avhich are exceptionally used are so used in the service of man, 

 and have thus become the subjects of artificial selection. 

 Thus " the great and inherited development of the udders in 

 coAvs and goats," quoted by Spencer from DarAvin, really affords 

 no proof of inheritance of the increase due to use, because, 

 from the earliest period of the domestication of these animals, 

 abundant milk-production has been highly esteemed, and has 

 thus been the subject of selection ; Avhile there are no cases 

 among Avild animals that may not be better explained by 

 variation and natural selection. 



Difficulty as to Co-adaptation of Parts by Variation and Selection. 



Mr. Spencer again brings forward this difficulty, as he 

 did in his Principles of Biology twenty -five years ago, and 

 lu'ges that all the adjustments of bones, muscles, blood-vessels, 

 and nerves Avhich Avould be required during, for example, the 

 development of the neck and fore-limbs of the girafie, could 



responding congenital diminution of the unused organ ; and in cases where 

 the means of nutrition are deficient, every diminution of these useless parts 

 will be a gain to the whole organism, and thus their complete disappearance 

 will, in some cases, be brought about directly by natural selection. This 

 corresponds with what we know of these rudimentary organs. 



It must, however, be pointed out that the non-heredity of acquired char- 

 acters was maintained by Mr. Francis Galton more than twelve years ago, on 

 theoretical considerations almost identical with those urged by Professor Weis- 

 mann ; while the insufficiency of the evidence for their hereditary trans- 

 mission was shown, by similar arguments to those used above and in the work 

 of Professor Weismann already referred to (see "A Theory of Heredity," in 

 Journ. Anthro}}. Instil., vol. v. pp. 343-34.^). 



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