ORGANIC GEOLOGICAL DYNAMICS. 567 



I need not stay to point out how extremely arbitrary every part of 

 this scheme is ; and how complex its machinery would be, even if it 

 did account for the facts. It may be sufficient to observe, as others 

 have done, 7 that the capacity of change, and of being influenced by 

 external circumstances, such as we really find it in nature, and there- 

 fore such as in science we must represent it, is a tendency, not to 

 improve, but to deteriorate. When species are modified by external 

 causes, they usually degenerate, and do not advance. And there is no 

 instance of a species acquiring an entirely new sense, faculty, or organ, 

 in addition to, or in the place of, what it had before. 



Not only, then, is the doctrine of the transmutation of species in 

 itself disproved by the best physiological reasonings, but the additional 

 assumptions which are requisite, to enable its advocates to apply it to 

 the explanation of the geological and other phenomena of the earth, 

 are altogether gratuitous and fantastical. 



Such is the judgment to which we are led by the examination of the 

 discussions which have taken place on this subject. Yet in certain 

 speculations, occasioned by the discovery of the Sivatherium, a new 

 fossil animal from the Sub-Himalaya mountains of India, M. Geoffrey 

 Saint-Hilaire speaks of the belief in the immutability of species as a 

 conviction which is fading away from men's minds. He speaks too 

 of the termination of the age of Cuvier, "la cloture du siecle cle 

 Cuvier," and of the commencement of a better zoological philosophy. 8 

 But though he expresses himself with great animation, I do not per- 

 ceive that he adduces, in support of his peculiar opinions, any argu- 

 ments in addition to those which he urged during the lifetime of 

 Cuvier. And the reader 9 may recollect that the consideration of that 

 controversy led us to very different anticipations from his, respecting 

 the probable future progress of physiology. The discovery of the 

 Sivatherium supplies no particle of proof to the hypothesis, that the 

 existing species of animals are descended from extinct creatures which 

 are specifically distinct : and we cannot act more wisely than in listen- 

 ing to the advice of that eminent naturalist, M. de Blainville. 10 

 " Against this hypothesis, which, up to the present time, I regard as 

 purely gratuitous, and likely to turn geologists out of the sound and 

 excellent road in which they now are, I willingly raise my voice, with 

 the most absolute conviction of being in the right." 



T Lyell, B. m. c. iv. 8 Compte Rendu de I'Acad. des Sc. 1837, No. 3, p 81. 

 See B. xvn. c. vii. 10 Compte Rendu, 1837, No. 5, p. 168. 



