CH. XXII] GEOGRAPHICAL DISTRIBUTION 231 



Cupressus macrocarpa at Monterey (p. 88), though this species 

 IS admirably suited to life in a climate a little damper. But it is 

 stretchmg our imaginations somewhat to imagine that most 

 localised species are suited only to the places in which they occur 

 Conditions change so much from year to year that unless a 

 species IS suited to a considerable range, it will not be able to 

 survive at all. It would not obtain a greater change by moving 

 to another locality not too far away. It is probable that the 

 slow acclimatisation practised by nature will ultimately ac- 

 custom species to widely different conditions, but loner" time 

 must be allowed. "^ 



The arithmetical facts disclosed in this book are much opposed 

 to any such supposition. It is almost impossible to suggest con- 

 ditions to which the overlapping species in the map on^^p. 56, or 

 the grouped species of varying size of area on p. 156, can be 

 suited. The point of view usually taken up on this matter has 

 been very well put by Huxley (59, p. 123), who says: 



"We are very much in the habit of tacitly assuming that 

 because certain plants and certain animals exist only under cer- 

 tain chmatal conditions, there is something in what' we vaguely 

 call the 'constitution' of the plant or animal which binds them 

 to these conditions, and renders it impossible for them to live 

 elsewhere. I wish we could get rid of this word 'constitution'; 

 for I take it to be one of the many verbal anodynes by which the 

 discomfort of ignorance is dulled." 



The arrangement of species in areas that are concentrated 

 about particular points, as is shown in the curves and maps on 

 pp. 79, 80, 153, 156. goes to show that local adaptation has had 

 little to do with the dispersal. If not locally adapted, the species 

 Mould die out Avithout spreading at all; but once established 

 they begin to spread, at an average rate determined by the 

 various factors that act upon them. The fact that the northern 

 invasion of New Zealand (cf. table on p. 77, and curves on pp. 79, 

 80) does not show any increase of local species at the region 

 where the southern invasion shows its maximum, and vice versa, 

 is a strong proof against local conditions having anything serious 

 to do with multiplication of species. 



The fourth and fifth suppositions, that species of small area, 

 and genera of one or few species, are dying out, are those most 

 strenuously adhered to, but in view of the facts set forth in tliis 

 book seem to form a very difficult position to uphold. It need 

 not be entirely abandoned, but in place of suj^posing fnost such 



