138 MR. DARWIN S WORK AND 



which now exist in the same country, you do not find 

 gigantic specimens of ant-eaters and kangaroos, but you 

 find rhinoceroses, elephants, lions, tigers, &c, — of differ- 

 ent 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 or- 

 ganic 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 T flourish. 



What meaning has this fact upon any other hypo- 

 thesis or supposition than one of successive modifica- 

 tion ? 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 ex- 

 pect 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 w T ith 

 almost any form of the doctrine of progressive modifi- 

 cation ; they would not be absolutely inconsistent with 

 the wild speculations of De Maillet, or with the less 

 objectionable hypothesis of Lamarck. But Mr. Dar- 



