90 Prof. A. Gray on Species considered as to 



the number of monstrosities annually produced, and the possi- 

 bility of their enduring, may be regarded as favourable to Heer's 

 view. 



As an index to the progress of opinion in the direction referred 

 to, it will be interesting to compare Sir Charles Lyell's well- 

 known chapters of twenty or thirty years ago, in which the per- 

 manence of species was ably maintained, with his treatment of 

 the same subject in a work just issued in England, which, how- 

 ever, has not yet reached us. 



A belief in the derivation of species may be maintained along 

 with a conviction of great persistence of specific characters. 

 This is the idea of the excellent Swiss vegetable palaeontologist, 

 Heer, who imagines a sudden change of specific type at certain 

 periods ; and it perhaps is that of Pictet. Falconer adheres to 

 somewhat similar views in his elaborate paper on Elephants, 

 living and fossil, in the ' Natural History Eeview ' for January 

 1863. Noting that " there is clear evidence of the true Mammoth 

 having existed in America long after the period of the northern 

 drift, when the surface of the country had settled down into its 

 present form,^^ and also in Europe so late as to have been a 

 cotemporary of the Irish Elk, and, on the other hand, that it 

 existed in England so far back as before the deposition of the 

 Boulder Clay, also that four well-defined species of fossil Ele- 

 phant are known to have existed in Europe, that " a vast num- 

 ber of the remains of three of these species have been exhumed 

 over a large area in Europe, and, even in the geological sense, 

 an enormous interval of time has elapsed between the formation 

 of the most ancient and the most recent of these deposits, quite 

 sufficient to test the persistence of specific characters in an Ele- 

 phant," he presents the question, " Do, then, the successive 

 Elephants occurring in these strata show any signs of a passage 

 from the older form into the newer V 



To which the reply is, " If there is one fact which is impressed 

 on the conviction of the observer with more force than any 

 other, it is the persistence and uniformity of the characters of 

 the molar teeth in the earliest known Mammoth and his most 



modern successor Assuming the observation to be correct, 



what strong proof does it not afibrd of the persistence and con- 

 stancy, throughout vast intervals of time, of the distinctive cha- 

 racters of those organs which are most concerned in the existence 

 and habits of the species ? If we cast a glance back on the long 

 vista of physical changes which our planet has undergone since 

 the Neozoic epoch, we can nowhere detect signs of a revolution 

 more sudden and pronounced, or more important in its results, 

 than the intercalation and sudden disappearance of the glacial 

 period. Yet the ' dicyclotherian' Mammoth lived before it, and 



