WINGLESS INSECTS 449 



marshes of N.S. Wales and Tasmania, but is not found wild 

 elsewhere out of Europe that I know of in the Southern 

 Hemisphere these are the extraordinary facts that will 

 not be accounted for. Out of full 800 species I do not 

 think that there are a dozen common to South-East and 

 South- West Australia ; whole well marked genera, containing 

 many sections and species, are absolutely confined to S.W. 

 Australia. There is nothing like this in any other part 

 of the world : it is utterly astounding, and though I thought 

 myself well up in the Australian Flora, I was not prepared 

 for this to such an extent. Also taken as a whole the Flora 

 of Tasmania does not present so many species hardly distinct 

 from S.E. Australia as it ought. The Tasmanian species are 

 either very distinct, or quite the same, and what is most 

 curious, this applies as well to the alpine plants, though the 

 climate of the Australian Alps must be a good deal different 

 from that of the Tasmanian ones. 



There is another point to be worked in your apterous 

 insect case viz., the proportion of apterous European species 

 in Madeira great or small. If over-sea migration were the 

 means of peopling Madeira with insects, then the European 

 species should be winged ones. There is still another point. 

 Do you suppose that the majority are apterous because the 

 winged ones have been blown out to sea and perished 

 miserably ? Eeally these questions are like Cerberus and 

 his heads the more arguments one disposes of the more 

 rise up in your way. 



Kew : November 9, 1856. 



I have finished the reading of your MS. [on Geog. Distrib.] 

 and have been very much delighted and instructed. Your 

 case is a most strong one and gives me a much higher idea 

 of change than I had previously entertained ; and though, 

 as you know, never very stubborn about unalterability of 

 specific type, I never felt so shaky about species before. The 

 first half you will be able to put more clearly when you polish 

 up. I have in several cases made pencil alterations in details 

 as to words, &c., to enable myself to follow better some of 

 it is rather stiff reading. I have a page or two of notes for 

 discussion, many of which were answered as I got further 

 with the MS., more or less fully. 



Your doctrine of the cooling of the tropics is a startling 



