TERTIARY FOSSILS. 



249 



reality, no stultification except in the critic's own mind. 

 It was not my scale which he refers to, but Dr. Fletcher's ; 

 adopted into my book, not as a plan of the actual process 

 of development, but as a general indication of the com- 

 parative organization of the animal orders. I do not con- 

 sider the assumed contemporaneousness of the carnivora 

 and monkeys (which the reviewer erroneously calls bima- 

 na) as at all contradictory of a true development theory, 

 for I regard them all as distinct lines of development, 

 which might well advance to a certain stage (namely, that 

 of the terrestrial mammala) about the same time. T am 

 not, however, entitled to blame the reviewer for thi a ob- 

 jection, as the idea of a development in a plurality of 

 lines must be new to him. 



" As we ascend," he says, " towards the middle divis- 

 ions of the [tertiary] series, there is a development of 

 nature's kingdom, nearer and nearer to living types. But 

 it is not a development after our author's scheme. It fol- 

 ows the law of he rise, progress, and decline of the fam- 

 ilies of the older world, already pointed out. We have 

 no confusion of genera and species, and no shades of struc- 

 ture to make dim their outlines." Now there is here an 

 acknowledgment, in which all geologists accord, of a 

 constant gradual approach to living types. Is not this, in 

 itself, a fact speaking strongly for some simply natural 

 procedure in the origin of the present tribes ? A change 

 goes on from one set of forms to another, ir the same way 

 as one human generation is changed for another — name- 

 ly, by the withdrawal of some and the addition of others, 

 until at length the whole personnel of one age is superse- 

 ded by that of another. The removal of old species is 

 the result, by our critic's own showing, of law; and laws 

 for the extinction of species are in operation at the pres- 

 ent day. Can we well suppose the rise of the new spe- 

 cies to be a phenomenon of an essentially different char- 

 acter ? for here is the whole question at issue. I say no 

 — any ideas I have ever acquired of philosophy, as an ex- 

 pression of our ascertainment of the order of nature or prov- 

 idence, forbid me to form such a conclusion. A ** con- 

 fusionPof genera or species" is not to be presumed; there 

 is no need for a shading of structure to make dim their 

 outlines. I suggest that aline of organization analogous 

 to the progress of the embryo of an elevated species had 

 passed in the course of time through its appointed stages 



