Remeivs — LyelVs Principles of Geology. 571 



selection. The tendency of species to multiply beyond the means 

 of subsistence, the struggle for life, and the conditions on which 

 " the survival of the fittest " depends, are explained. The opinions 

 of Linnaius, De Candolle, and Darwin on species, are compared, and 

 it is show^n that alternate generation will not explain the mode of 

 the origin of new species. 



Chapter 38 is devoted to the consideration of the geographical dis- 

 tribution of species. The six great provinces of distinct species of 

 terrestrial mammalia are chiefly dwelt upon, and the agreement of 

 the limitation of the species of birds and reptiles, and even of the 

 invertebrate animals generally, to the same regions is pointed out. 



In chapter 39 is given an account of the migration and diffusion 

 of terrestrial animals, slightly added to and corrected, from the 

 ninth edition. 



In the 40th chapter, on the geographical distribution and migration 

 of fish, testacea, insects and plants, several additions and alterations 

 have been made, e.g. : — On the species of marine shells and fishes 

 on opposite sides of the Isthmus of Panama ; Moths seen flying 

 300 miles from land ; Sir C. Bunbury on plants of the Table-land of 

 Brazil ; Darwin on seeds and fruits immersed in salt water without 

 injury; Eobert Brown on the source of the gulf- weed, or Sargassum; 

 Darwin on seeds transported by birds. 



The 41st chapter is a new essay, and treats of insular floras and 

 faunas, considered with reference to the origin of species. The 

 islands of the Eastern Atlantic, especially the Madeiras and 

 Canaries, their volcanic origin and Miocene age, are first treated of 

 and then the extent to which the species of mammalia, birds, in- 

 sects, land-shells, and plants, agree or do not agree with continental 

 species. The identity, or non-identity, also, of species of all these 

 classes found in different archipelagos, or in different islands of the 

 same archipelago, is shown to bear an unmistakable relation to the 

 facilities enjoyed by each class of crossing the ocean. The bearing 

 of this relationship on the theory of the origin of species, by varia- 

 tion and natural selection, is pointed out. 



The 42nd chapter treats of the extinction of species, among the 

 additions to which may be mentioned the following : — Dr. Hooker, 

 on extermination of plants in St. Helena, and Mr. Travers on the 

 spread of foreign plants in New Zealand. 



The whole of the 43rd chapter, on man, considered with reference 

 to his origin and geographical distribution, is new, save the first 

 five pages. 



The antiquity of the more marked human races, and the coinci- 

 dences of their geographical range with that of the chief zoological 

 provinces, is considered. The question as to the multiple origin of 

 man is discussed. The bearing of the theory of progressive deve- 

 lopment and of Darwin's theory of natural selection on the deriva- 

 tion of man from the inferior animals is treated of. Some remarks 

 on submarine forests at Bournemouth, on the south coast of Hampshire, 

 and the Bay of Fundy, are added. 



A brief sketch is given, in retrospective chronological order, of 



