TERTIARY FOSSILS. 



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 oi 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. I am 

 not, however, entitled to blame the reviewer for thi" 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- 

 fusion of genera or species" is not to be presumed; there 

 is no need for a shading of structure to make dim f.heir 

 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 



