Ixvi PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



that have taken place in the land, in many places, since the creation 

 of species now living. Thus in chapter 11 of the first edition of 

 the second volume of the ' Principles of Geology,' published in 

 1832, we find the following passages : — " We have pointed out in the 

 preceding chapters the strict dependence of each species of animal 

 and plant on certain physical conditions in the state of the earth's 

 surface, and on the number and attributes of other organic beings 

 inhabiting the same region. We have also endeavoured to show 

 that all these conditions are in a state of continual fluctuation, the 

 igneous and aqueous agents remodelling, from time to time, the phy- 

 sical geography of the globe, and the migrations of species causing 

 new relations to spring up successively between different organic 

 beings." " As considerable modifications in the relative levels of 

 land and sea have taken place in certain regions since the existing 

 species were in being, we can feel no surprise that the zoologist and 

 botanist have hitherto found it difficult to refer the geographical dis- 

 tribution of species to any clear and determinate principles, since 

 they have usually speculated on the phaenomena, upon the assumption 

 that the physical geography of the globe had undergone no material 

 alteration since the introduction of the species now living *." In the 

 9th chapter of the third volume of the same work, published in 1833, 

 the following observations occur at p. 115. Treating of the migra- 

 tion of animals and plants, he says, " A large portion of Sicily has 

 been converted from sea to land since the Mediterranean was peo- 

 pled with the living species of testacea and zoophytes. The newly 

 emerged surface, therefore, must, during this modern zoological epoch, 

 have been inhabited for the first time with the terrestrial plants and 

 animals which now abound in Sicily. It is fair to infer, that the ex- 

 isting terrestrial species are, for the most part, of as high antiquity 

 as the marine ; and if this be the case, a large proportion of the plants 

 and animals, now found in the tertiary districts in Sicily, must have 

 inhabited the earth before the newer pliocene strata were raised above 

 the waters. The plants of the flora of Sicily are common, almost 

 without exception, to Italy or Africa, or some of the countries sur- 

 rounding the Mediterranean, so that we may suppose the greater part 

 of them to have migrated from pre-existing lands, just as the plants 

 and animals of the Phlegraean fields have colonized Monte Nuovo, 

 since that mountain was thrown up in the sixteenth century. We 

 are brought, therefore, to admit the curious result, that the flora 

 and fauna of the Val di Noto, and some other mountainous regions of 

 Sicily, are of higher antiquity than the country itself, having not 

 only flourished before the lands were raised from the deep, but even 

 before they were deposited beneath the waters." 



We have seen that the great geological conditions to which Pro- 

 fessor Forbes refers are — 1st, the existence of land above the waters 

 during the Miocene epoch, and of sea between the northern coast of 

 Spain and the British Islands ; 2ndly, the formation of deposits in 

 that Miocene sea, and the subsequent elevation of that sea-bottom 

 above the waters, extending over the whole Mediterranean region, and 

 ^ Pages 182 and 183. 



