ZOOLOGY. 357 



over the lands which we inhabit. At the period of such migrations, 

 this island (England) was still united with the continent ; but a large 

 number of the existing species of raollusca, and some other tribes of 

 marine animals, can claim a much higher antiquity ; so much so, that 

 they were already created during the drift or glacial epoch, when the 

 physical geography of Europe bore no resemblance to that now estab- 

 lished. If, therefore, ten or twenty thousand years were added to the 

 chronology of the human period, it would still constitute a mere fraction 

 of that vast geological division of time during which the species, now 

 our contemporaries, have been coming into existence. But how small 

 is the progress yet made by us in ascertaining the order in which the 

 mammalia now living were created ! Some species are so ancient as 

 to have coexisted with a fauna of which nearly all the species have 

 died out ; while others may be coeval in their origin with man, and a 

 few, perhaps, of a more recent creation. Man himself has been mul- 

 tiplying on the earth since he entered upon it, and enlarging the range 

 of many animals, both intentionally and against his will. These species 

 occupy, together with the human population, the places left vacant by 

 such as are exterminated from time to time. Y\ r hether the amount of 

 change in those ten or twenty thousand years which immediately pre- 

 ceded our own times, has been greater or less than the average muta- 

 tion during equal periods of the pnst, from the Silurian to the Pliocene 

 era, is a point on which, in the present infancy of the science, it would 

 be idle to speculate. Of this, however, we may feel assured, that the 

 greater the identity of the system of terrestrial changes, present and 

 luture, organic and inorganic, with that which has prevailed through- 

 out past time, the more faithfully shall we be able to interpret the rec- 

 ords of creation which are written on the framework of the globe. 



In the first publication of the Huttonian theory, it was declared that 

 we can neither see the beginning nor the end of that vast scries of phe- 

 nomena which it is our business, as geologists, to investigate. After 

 sixty years of renewed inquiry, and after we have greatly enlarged the 

 sphere of our knowledge, the same conclusion seems to me to hold 

 true. But, if any one should appeal to such results in support of the 

 doctrine of an eternal succession, I may reply that the evidence has 

 become more and more decisive in favor of the recent origin of our own 

 species. The intellect of man, and his spiritual and moral nature, are 

 the highest works of creative power known to us in the universe ; and 

 to have traced out the date of their commencement in past time, to 

 have succeeded in referring so memorable an event to one out of a 

 long succession of periods, each of enormous duration, is perhaps a more 

 wonderful achievement of science, than it would be to have simply dis- 

 covered the dawn of vegetable or animal life, or the precise time when, 

 out of chaos, or out of nothing, a globe of inanimate matter was formed. 

 Sir Charles LyelVs Address before the Royal Geological Society. 



DOCTRINE OF SPECIFIC ORGANIC CENTRES. 



THE actual zoology and botany of the earth's surface exhibit several 

 distinct regions, in each of which the indigenous animals and plants 



