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impediment to insect progress), — but they are of 

 secondary importance, when compared with marine and 

 alpine ones ; and their consequences may be, to a certain 

 extent, deduced from the considerations which I have 

 just entered into. My main object has been to draw 

 attention to the fact, that the great obstacles which 

 Nature has placed agaiast the too rapid dispersion 

 of animal Hfe should be more strictly taken into account 

 (as a matter of positive reality) than it is, during our 

 investigations iato entomological geography. To be 

 aware that these barriers exist, and yet to feel surprised, 

 especially ia a country where the species are principally 

 wingless, that we do not discover indications of a general 

 uniformity ia its fauna, involves an absurdity, — unless 

 the doctrine of specific centres of creation be a mere 

 coiaage of the brain. But, if we believe in that theory 

 (which, untd it can be shown to be impossible, I hold 

 that we are a priori bound to do), we must at least act 

 consistently with ourselves, and not anticipate phseno- 

 mena where we have neither reason nor right to look 

 for them. 



We are too apt to draw a line of imaginary demarca- 

 tion between the sciences, as though each had its own 

 propositions to establish, and nothing more : indeed, 

 some of us would appear to assume (though perhaps 

 tacitly), that what is proved to be tme iu one depart- 

 ment may be, at least, rendered inconsistent (if not 

 actually negatived) in another. But surely this requires 

 no argument to refute, — since a principle which is triie. 



