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universal ocean at a remote period after the planet had become the abode of 

 living creatures. But few will now deny that the proportion of sea and land 

 approached very nearly to that now established long before the present species 

 of plants and animals had come into being. 



"The reader must bear in mind that the language of Buffon, in 1755, 

 respecting ' natural barriers ' which has since been so popular, would be wholly 

 without meaning had not the geographical distribution of organic beings led 

 naturalists to adopt very generally the doctrine of specific centres, or, in other 

 words, to believe that each species, whether of plant or animal, originated in a 

 single birthplace. Reject this view, and the fact that not a single native quad- 

 ruped is common to Australia, the Cape of Good Hope, and South America, 

 can in no ways be explained by adverting to the wide extent of intervening 

 ocean, or to the sterile deserts, or the great heat or cold of the climates, through 

 which each species must have passed, before it could migrate from one of those 

 distant regions to another. It migbt fairly be asked of one who talked of 

 impassable barriers, why the same kangaroos, rhinoceroses, or lamas, should 

 not have been created simultaneously in Australia, Africa, and South America 1 ? 

 The horse, the ox, and the dog, although foreign to these countries until 

 introduced by man, are now able to support themselves there in a wild state ; 

 and we can scarcely doubt that many of the quadrupeds at present peculiar to 

 Australia, Africa, and South America, might have continued in like manner 

 to inhabit all the three continents, had they been indigenous in each, or 

 could they once have got a footing there as new colonists." 



I might multiply quotations from these and other authors occupying the 

 foremost rank in the scientific world, in order to show that both sea and land 

 may, in the present condition of organic nature in every part of the globe be 

 properly divided into what have been termed distinct Zoological and Botanical 

 Provinces, each occupied by special groups of animals and plants which, 

 however, have been found to exhibit, in each case, a certain amount of 

 coincidence in range of species ; and, indeed, it is urged, that no hypothesis 

 respecting the origin of species can possibly be satisfactory, which does not 

 show, in the first place, how species and genera, and ofter larger groups, now 

 range in space in such a manner as to lead to the implication that they have 

 spread from a limited area termed a " centre of creation," until their progress 

 has been stopped either by some physical barrier or other condition hostile to 

 further extension ; and which does not account, in the next place, for the 

 restriction of peculiar generic forms to certain pai'ts of the globe. 



There is nothing more striking to the naturalist, moreover, than the fact, 

 now well determined, that the rules established by observation in regard to the 

 distribution of living organisms are those which have also been found to obtain 

 in regard to fossil forms, and it has thence been fairly argued, and as I believe 

 sufficiently well proved, that the intimate connection observed between the 

 existing and the fossil forms within each particular province points to the 

 certainty that the former are of derivative origin, and are not primordial or 

 independent creations. I am compelled, having regard to the length of a 

 lecture, arbitrarily to limit my observations upon this part of the subject, but 

 I think that even without going into the reasons urged by Mr. Darwin and 

 others, as to the improbability of our being able to identify the actual fossil 

 ancestor of any living species, or to trace its descent through past geological 

 epochs, I have sufficiently shown to you the probability that the forms of life 

 now occupying any particular Zoological or Botanical Province may be looked 

 upon as the descendants of those which have occupied it during past geological 

 periods, and that the differences between the existing and fossil forms are due 

 to the opei'ation of the laws so clearly expounded by Mr. Darwin. Of course 

 in assuming such a probability, time becomes an important factor, and those 



