1922.] C/taraders in .^omr f'/iaradri'me (iciiera. 477 



Tundras are and were presunuibly always associated with 

 glacial conditions, and the various glacial onsets coincided 

 with the Pleistocene, as far, at any rate, as the Northern 

 Hemisphere and our immediate thesis is concerned. If, 

 therefore, it is held that the colour-pattern typical of the 

 Golden-Plover Association was th(^ direct outcome of a 

 resj)on?e to the tundral environment, it follows that this 

 colour-pattern is no older than the Pleistocene. It is, 

 of course, impossible to prove the contrary. Colour-patt(n-n 

 in any particuhir phylum or group may have been, in the 

 past, changeable and evanescent ; yet, from the evidence 

 which I shall presently produce, and from evidence which 

 I have already produced *, there seems every reason to 

 suspect that it may be even more persistent than bon}' 

 structural characters ; while as to the persistence of these 

 last in birds, one has only to examine the series of fossil 

 Limicola:' in the British Museum Collection to be deeply 

 impressed — characters, for instance, may still be reproduced 

 in the head of a humerus of, let us say, an Eroliine or 

 Tringine form of the present day which are. in the most 

 minute degree, comparable to those of a like form as far 

 back as the Miocene (say three or four million years ago). 

 The characters, for instance, which differentiate the humerus 

 of a fossil Miocene Plover from a Miocene Gull are amazingly 

 similar to those of presont-day forms. 



]f, then, we may presume, as I think we are entitled, that 

 the colour-pattern characteristic of the " Golden-Plover 

 Association" is older than the Pleistocene, it might well 

 be asked where were situated the Miocene or Pliocene 

 Tundras to fix such a colour-pattern (by the usually ac- 

 cepted means of natural selection and the survival of the 

 fittest); for a study of the fossil Tertiary flora in circum- 

 polarand arctic regions does not suggest tundral conditions : 

 and we know that all through the Tertiary, Euro])e, at any 

 rate, enjoyed a mild and at first even a tropical or a su))- 

 tropical climate. 



* Ibis. 1914, pp. ;«t9-403: 1915, pp. 3'JO '?A(\. 



