APPENDIX A. 



ON THE EXTINCTION OF SPECIES. 



Being the Conclusion of the Fuller ian Course of Lectures on 



Physiology, for 1859. 



IN a Report to the British Association for the Advancement of 

 Science, On the Extinct Mammals of Australia, published in the 

 Volume of Reports for 1844, evidence is adduced in proof of the 

 law, that with extinct as with existing mammalia particular forms 

 were assigned to particular provinces, and that the same forms 

 were restricted to the same provinces at a former geological period 

 as they are at the present day. That period, however, was the 

 more recent tertiary one. 



In carrying back the retrospective comparison of existing and 

 extinct mammals to those of the eocene and oolitic strata, in rela- 

 tion to their local distribution, we obtain indications of extensive 

 changes in the relative position of sea and land during those epochs, 

 through the degree of incongruity between the generic forms of the 

 mammalia which then existed in Europe, and any that actually 

 exist on the great natural continent of which Europe now forms 

 part. It would seem, indeed, that the further we penetrate into 

 time for the recovery of extinct mammalia, the further we must 

 go into space to find their existing analogues. To match the eo- 

 cene palceotheres and lophiodons we must bring tapirs from Suma- 

 tra or South America; and we must travel to the antipodes for 

 myrmecobians, the nearest living analogue to the amphitheres and 

 spalacotheres of our oolitic strata. 



On the problem of the extinction of species I have little to say ; 

 and of the more mysterious subject of their coming into being, 

 nothing profitable or to the purpose. As a cause of extinction in 

 times anterior to man, it is most reasonable to assign the chief 

 weight to those gradual changes in the conditions affecting a due 

 supply of sustenance to animals in a state of nature which must 

 have accompanied the slow alternations of land and sea brought 



