THE CHIEF OOLEOPTEROtrS EiLUNiE. 47 



favour of this Australian connexion having been the source of 

 the microtypal Coleopterous element in Caffraria, it may be said 

 that it seems to be most pronounced on the eastern coast of 

 South Africa ; against it that the element, if filtered through Aus- 

 tralia, should have been more modified from the original northern 

 type than it seems to be. 



So far as regards the submerged Patagonian continent in ques- 

 tion, I think we may, from the paucity of the traces left of its 

 inhabitants, come to the conclusion that its duration, as compared 

 with that of other continents, had not been long. It must have 

 taken a long time for insects slowly to have spread from Africa 

 to South America ; but it seems to me that where there are no 

 exceptional causes of fertilitj'^ (as where a limestone or chalk sea- 

 bottom was upraised, which I imagine, from being composed 

 partly of organic matter, would be more speedily fertilized), where, 

 for example, the bottom was sandy or shingly, as in Patagonia, or 

 sandy, as in the Sahara, and where there is no water running 

 through it, the process and rate of rapidity of clothing it with soil 

 and vegetation must, cceteris paribus, be nearly the same in all, 

 and that we may form an estimate of the comparative age of a 

 country by the degree of fertility of its deserts. Thus I should 

 suppose the Kalahari desert, which, although called a desert, is 

 not wholly a waste, but studded with tufts of plants, must be older 

 than the Salt-Lake deserts in North-west America, which are only 

 beginning to get a widely scattered dotting of sage plants, and 

 these deserts again to be older than the Sahara, which has no 

 vegetation at all upon it. . It is true that the conditions of the 

 Sahara are exceptionally unfavourable ; but I take it there is some 

 truth under the idea. So judged, the Patagonian continent could 

 not have been proportionately far advanced, judging from its 

 inhabitants, when it again sunk out of view. 



Polynesia has hitherto been an entomological puzzle ; and one 

 of our most eminent British entomologists lately told me that 

 after poring over the lists of its species and making them up into 

 tables on various principles, he had at last been driven to the con- 

 clusion that they were composed of the sweepings of the whole 

 world, and that there was no other way of accounting for them but 

 by the supposition tbat the Pacific islands have had a dip under 

 the sea long enough to kill all life, and that what was now found 

 on it was derived from subsequent colonization after their reap- 

 pearance, drawn, like its sailors, from all quarters of the globe. 



