THE CHIEF COLKOL'TEItOUS IfAUNiE. 



7 



spots A and B, and nowhere else ; but the moment we find 

 another supposed relic, species No. 2, also left in A and B, and 

 nowhere else, doubt assails us, and increases in an inverse ratio 

 with the occurrence of every additional relic. 



The fourth supposition is, I think, the true one, namely, 

 continuity of soil at some former period ; and upon that as a 

 basis I rest the propositions I am about to submit. Upon it, I 

 think, I can explain satisfactorily many of the remarkable in- 

 stances of peculiar geographical distribution which have hitherto 

 defied the ingenuity of naturalists to solve, and notably that 

 which I have first set before me, viz. the resemblance which 

 species from the temperate regions of the northern hemisphere 

 bear to those from similar latitudes in the southern hemisphere. 

 With the help of the above postulate I can trace the links 

 all the way from the one to the other plainly in insects, plants, 

 and land-shells, and more imperfectly in the higher animals ; but 

 also in them, if allowance be made for the greater variability in 

 form in the higher animals under change of condition of life, 

 and their distribution be examined in relation to the geographical 

 epochs in which the different forms respectively came into being 

 and most prevailed. The absence of particular mammals in a 

 particular land cannot vitiate my theory, if the distribution of 

 animals in it had been completed before the mammals appeared. 



For the better understanding of my argument I shall first 

 state the results at which I have arrived. 



The position I am about to maintain then is, that, subject to 

 modifications to be afterwards mentioned, all the Coleoptera in 

 the world are referable to one or other of three great stirpes. 

 These three no doubt originally sprung from one stirps, and ac- 

 quired their distinguishing features by long-continued isolation 

 from each other, combined with changes in their conditions of 

 life. But now we have three, and only three, great strains, 

 sometimes intermingling with each other, sometimes underlying 

 or overlying each other, and sometimes developed into new 

 forms, but always distinguishable and traceable to one or other 

 of the three sources. 



These are — 1, the Indo- African stirps ; 2, the Brazilian stirps ; 

 and 3, what, for want of a better name, I shall call the micro- 

 typal stirps, in allusion to the general run of the species com- 

 posing it being of a smaller size, or, more strictly speaking, not 

 containing such large or conspicuous insects as the others. It 



