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SO great in the organization that dry cows may be brought to the 

 pail. Under these circumstances the variety remains permanent 

 as it is driven to the limit line of species by the necessities of 

 condition. Thus permanent varieties^ as they are called^ arise out 

 of the law of perpetuity of species. 



The time required to effect tliese changes in a race, is to be 

 measured by successive generations rather than by years. Thus 

 we have seen degeneration, as it is called, to occur most readily 

 in swine, whose generations in this country may be Counted almost 

 or quite as many as their years, our native breed being removed 

 from its European origin some two hundred generations. That 

 of horses and neat cattle is perhaps one hundred — a period that 

 experience has shown to be long enough to produce essential 

 variations. Now, supposing the average generations of man to be 

 periods of thirty years, we should require 6,000 years to cover an 

 extent equal to the existence of swine in America, so that the 

 fact often adverted to, that the negro of the ancient sculptures is 

 recognized by the present peculiarities of the African race, does 

 not disprove the common origin of men. 



In the original plan universal dominion was given to no one 

 species, either in the vegetable or animal world, but by multipli- 

 city of forms, adapted to a multiplicity of ends, greater aggregate 

 results were attained. . The same law also holds among varieties, 

 each having its origin in its peculiar fitness for some purpose. 

 This is very clear in the case of dogs, horses and horned cattle, 

 and it is curious to notice that in this way Nature points out the 

 practice of specialties as the great effective means of civilization. 



But there are many causes which produce a variation of form 

 in animated nature of which we are yet ignorant, and which are 

 consequently said to be accidental. Thus, occasionally, an indi- 

 vidual is born among northern nations with sandy hair and a 

 very fair skin. When exposed to the rays of the sun, instead of 

 " tanning," or becomming dark, his skin inflames, and even 

 blisters. Though such individuals have always existed among 

 northern nations, yet they have not been lost in the uniform type, 

 but are continually reappearing, marked with all possible distinct- 

 ness. The same is equally true of the albinos and of the six- 



