326 



KATUEAL SELECTION. 



[Ch. XXXVII. 



derivation of species in general from the mixture of a limited 

 nmnber of original stocks^ differing widely from each other 

 all our experience is against such an hypothesis ; for between 

 plants or animals of veiy distinct genera we can obtain 

 no cross-breeds. " Nor is it easy to comprehend how sjoecies 

 of intermediate character between two divergent types could 

 give rise to a mongrel offspring having qualities and instincts 

 fitting them to hold their ground in the struggle for life. 



If we take some genus of insects, such as the bee, we find 

 that each of the numerous species has some difference in its 

 habits, its mode of collecting honey, or constructing its 

 dwelling, or providing for its young, and other particulars. 

 In the case of the common hive bee, the workers are described 

 by Kirby and Spence, as being endowed with no less than 

 thirty distinct instincts.^ So also we find that, amono-st a 



numerous 



mode 



When 



recollect how 



com 



are the relations of 



these instincts with co-existing species, both of the animal 



in<zdoms 



tliat a bastard race could sirring- from the uiiion of these 

 species, and retain iust so 



much 



of each 



parent stock as to preserve its ground in spite of the dano-ers 



which surround it. 



The theory of the origin of species by variation and natural 

 selection, would be untenable unless we could assign very 

 different degrees of antiquity to the generic and ''specific 



types now existing. fcJome of them must date from remote 

 geological periods, others must be comparatively modern. 

 Of this last class are those forms of which the living re- 

 presentatives run so much the one into the other "that 

 scarcely any two naturalists can agree as to where the lines 

 of demarcation between the species ought to be drawn. 

 The British roses present a familiar illustration of this 

 ambiguous state of things, Mr. Bentham making only five 

 species of them, and Dr. Babington seventeen. Mr. Darwin 

 sees in this abundance of closely allied species an active 



* Intr. to Entom. vol. ii. p. 504, ed. 1817. 



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