106 MR. DARWIN'S WORK AND 



find rhinoceroses, elephants, lions, tigers, etc., of different 

 species to those now living, but still their close allies. If 

 you turn to South America, where, at the present day, we 

 have great sloths and armadilloes and creatures of that 

 kind, what do you find in the newest tertiaries ? You 

 find the great sloth-like creature, the Megatherium, and 

 the great armadillo, the Glyptodon, and so on. And if you 

 go to Australia you find the same law holds good, namely, 

 that that condition of organic nature which has preceded 

 the one which now exists, presents differences perhaps of 

 species, and of genera, but that the great types of organic 

 structure are the same as those which now flourish. 



What meaning has this fact upon any other hypothesis 

 or supposition than one of successive modification ? But 

 If the population of the world, in any age, is the result 

 of the gradual modification of the forms which peopled 

 it in the preceding age, if that has been the case, it is 

 intelligible enough ; because we may expect that the 

 creature that results from the modification of an elephantine 

 mammal shall be something like an elephant, and the 

 creature which is produced by the modification of an 

 armadillo-like mammal shall be like an armadillo. Upon 

 that supposition, I say, the facts are intelligible ; upon 

 any other, that I am aware of, they are not. 



So far, the facts of palaeontology are consistent with 

 almost any form of the doctrine of progressive modification ; 

 they would not be absolutely inconsistent with the wild 

 speculations of De Maillet, or with the less objectionable 

 hypothesis of Lamarck. But Mr. Darwin's views have 

 one peculiar merit ; and that is, that they are perfectly 

 consistent with an array of facts which are utterly incon- 

 sistent with and fatal to, any other hypothesis of progressive 

 modification which has yet been advanced. It is one 

 remarkable peculiarity of Mr. Darwin's hypothesis that it 

 involves no necessary progression or incessant modification, 

 and that it is perfectly consistent with the persistence 

 for any length of time of a given primitive stock, con- 

 temporaneously with its modifications. To return to 

 the case of the domestic breeds of pigeons, for example ; 

 you have the Dove-cot pigeon, which closely resembles 

 the Rock pigeon, from which they all started, existing 

 at the same time with the others. And if species are 

 developed in the same way in nature, a primitive stock 

 and its modifications may, occasionally, aJJ find the con- 



