

BOOK IV 



THE VARIATION OF SPECIES IN SPACE AND TIME 



THE tendency of species towards variation has 

 been, since the very origin of the transformist 

 hypothesis, the starting-point and the strongest 

 foundation of this doctrine. But it is necessary, 

 at the outset, to make a distinction of great im- 

 portance between variation in space, that is the 

 variation of a species at a given moment whether 

 of the present epoch or of past times and varia- 

 tion in time, that is, the changes in species in the 

 series of successive strata of the earth's crust. 



CHAPTER XIV 



VARIATION IN SPACE AT THE PRESENT EPOCH 



Examples of variation in living species Variation among Land 

 Molluscs : Groups of forms, of varieties, local races, and modes of 

 variation. 



THE variability of existing species, already well 

 studied by Lamarck, has especially been brought 

 to light by the memorable observations of Darwin 

 on the races of domestic animals, as well as on wild 

 species. These are classical data to which I shall 

 not further refer. I have, likewise, in a previous 

 chapter, recalled the remarkable facts of specific 

 variation instanced by Neumayr in several genera 



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