so CIIAEACTEK OF Ciiap. 1. 



expect often to find a generic amount of difference in our do- 

 mesticated races. 



In attempting to estimate tlie amount of structural difler- 

 encc between the domestic races of the same species, we are 

 soon involved in doubt, from not knowing whether they have 

 descended from one or several parent-species. This point, if 

 it could be cleared up, would be interesting ; if, for instance, 

 it could be shown that the grevhound, bloodhound, terrier, 

 spaniel, and bull-dog, which we all know propagate their kind 

 so truly, were the offspring of any single species, then such 

 facts would have great weight in making us doubt about the 

 immutability of the many very closely-allied natural species — 

 for instance, of the many foxes — inhabiting different quarters 

 of the Avorld. I do not believe, as we shall presently see, that 

 the whole amount of difference between the several breeds of 

 the dog has been produced under domestication ; I believe 

 that some small part of the difference is due to their having 

 descended from distinct species. In the case of strongly- 

 marked races in some other domesticated species, there is 

 presumptive, or even strong, evidence that all are descended 

 from a single wild stock. 



It has often been assumed that man has chosen for domes- 

 tication animals and plants having an extraordinary inherent 

 tendency to var}^, and likewise to withstand diverse climates. 

 I do not dispute that these capacities have added largely to 

 the value of most of our domesticated productions ; but how 

 could a savage possibly know, when he first tamed an animal, 

 M'hether it would vary in succeeding generations, and whether 

 it would endure other climates ? Has the little variability of 

 the ass and goose, or the small power of endurance of warmth 

 by the reindeer, or of cold by the common camel, prevented 

 their domestication ? I cannot doubt that if other animals and 

 plants, equal in number to our domesticated productions, and 

 belonging to equally diverse classes and countries, were taken 

 from a state of nature, and could be made to breed for an equal 

 number of generations under domestication, they would on an 

 average vary as largely as the parent-species of our existing 

 domesticated productions have varied. 



In the case of most of our anciently-domesticated animals 

 and jilants, it is not possible to come to any definite conclusion, 

 whether they are descended from one or several wild species. 

 The argiunent mainly relied on by those who believe in the 

 multiple origin of our domestic animals is, that we find in the 



