vii CREATION BY LAW 161 



cannot be further developed in the same direction. Variation 

 seems to have reached its limits in these birds. But so it has 

 in nature. The fantail has not only more tail feathers than 

 any of the three hundred and sixty existing species of pigeons, 

 but more than any of the ten thousand known species of birds. 

 There is, of course, some limit to the number of feathers of 

 which a tail useful for flight can consist, and in the fantail we 

 have probably reached that limit. Many birds have the 

 oesophagus or the skin of the neck more or less dilatable, but 

 in no known bird is it so dilatable as in the pouter pigeon. 

 Here again the possible limit, compatible with a healthy 

 existence, has probably been reached. In like manner tho 

 differences in the size and form of the beak in the various 

 breeds of the domestic pigeon is greater than that between 

 the extreme forms of beak in the various genera and sub- 

 families of the whole pigeon tribe. From these facts, and many 

 others of the same nature, we may fairly infer that if rigid 

 selection were applied to any organ, we could in a comparatively 

 short time produce a much greater amount of change than 

 that which occurs between species and species in a state of 

 nature, since the differences which we do produce are often 

 comparable with those which exist between distinct genera or 

 distinct families. The facts adduced by the writer of the 

 article referred to, of the definite limits to variability in certain 

 directions in domesticated animals, are, therefore, no objection 

 whatever to the view that all the modifications which exist in 

 nature have been produced by the accumulation, by natural 

 selection, of small and useful variations, since those very 

 modifications have equally definite and very similar limits. 



Objection to the Argument from Classification 

 To another of this writer's objections that by Professor 

 Thomson's calculations the sun can only have existed in a 

 solid state 500,000,000 of years, and that therefore time 

 would not suffice for the slow process of development of all 

 living organisms it is hardly necessary to reply, as it cannot 

 be seriously contended, even if this calculation has claims to 

 approximate accuracy, that the process of change and develop- 

 ment may not have been sufficiently rapid to have occurred 

 within that period. His objection to the classification argu- 



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