88 OBJECTIONS TO THE HYPOTHESIS [pt. i 



already been successfully used in this way nearly a hundred 

 times. Nor, again, can it explain such cases as Castelnavia, -with 

 seven species in an area where there are no differences in con- 

 ditions (126, p. 15). Above all, it will not explain the mechanical 

 way in wliich every group of species behaves like every other, 

 as has been pointed out above. 



The next group of objections takes the general position that 

 endemics are mostly the relics of pre-existing floras ; the first is 

 (22) that endemics are usually rehcts in the sense of species that 

 are dying out; that they are old species driven into qiiiet nooks 

 or odd corners ; the most recent statement to this effect is that 



Very many endemics owe their limited distribution to the cir- 

 cunistance that they are remnants of comparatively vuisuccessful 

 types which have been exterminated elsewhere, and which even 

 in these isolated floras are waging a losing fight against more 

 vigorous and adaptable newcomers. 



This is undoubtedly true of a great number here and there 

 especially in the north temperate zone (particularly North America 

 and China), where the influence of the last glacial period was 

 severely felt, and so far as the first jiart of the sentence (to 

 "elsewhere") is concerned. We know from geological evidence 

 that in the Canaries and Madeira there are many generic sur- 

 vivals of the Tertiary flora now extinct in Europe itself, but we 

 have no proof that they are dying out there without change of 

 conditions. Age and Area has always insisted upon the reserva- 

 tion "so long as conditions remain reasonably constant," though 

 critics and opponents frequently ignore this. Guppy has re- 

 cently (50) shown that the endemics of the Canaries which may 

 be looked upon as Tertiary relics occupy more space in the 

 Canaries than do the more recent Mediterranean type of en- 

 demies, while they also extend to the Azores or Madeira, which 

 the latter do not. As these Tertiary relics are mainly woody, the 

 conditions are naturally against them so soon as man has settled 

 in the covmtry (cf. p. 27). 



When a species is really dying out, the fact is usually due to 

 some change of conditions; and, as we have shown above, dis- 

 persal is usually so slow and to such small distances that the 

 species may easily be cut off by the changing conditions, and 

 then gradually exterminated, through no fault of its own. 

 Cupressus macrocarpa is probably the most generally suitable 

 Conifer for average sub-tropical climates, and is planted in 

 milhons all over the warmer parts of the world ; yet it is dying 



