218 A.MARCKIAN HYPOTHESIS OF THE 



in the second place, in order to the reception of the theory, 

 that the area of the earth's surface occupied by the British 

 islands and the neighbouring coasts of the Continent once 

 stood fifty fathoms higher, in relation to the existing sea-level, 

 than it does now, — a belief which, whatever its specific 

 grounds or standing in this particular case, is at least in strict 

 accordance with the general geological phenomena of subsi- 

 dence and elevation, and which, so far from outraging any 

 experience founded on observation or testimony, runs in the 

 same track with what is known of wide areas now in the 

 course of sinking, like that on the Italian coast, in which the 

 Bay of Baise and the ruins of the temple of Serapis occur, 

 or that in Asia, which includes the Bun of Cutch ; or of 

 what is known of areas in the course of rising, like part of 



originated in, and was diffused from, a single primitive centre ; and that 

 there were numerous such centres situated in different parts of the world, 

 each centre being the seat of a particular number of species. They thus 

 admit great vegetable migrations, similar to those of the human races. 

 Those who adopt the latter view recognise in the distribution of plants 

 some of the last revolutions of our planet, and the action of numerous 

 and varied forces which impede or favour the dissemination of vege- 

 tables in the present day. They endeavour to ascertain the primitive 

 flora of countries, and to trace the vegetable migrations which have 

 taken place. Daubeny says that analogy favours the supposition that 

 each species of plant was originally formed in some particular locality, 

 whence it spread itself gradually over a certain area, rather than that 

 the earth was at once, by the fiat of the Almighty, covered with vegeta- 

 tion in the manner we at present behold it. The human race rose from 

 a single pair ; and the distribution of plants and animals over a certain 

 definite area would seem to imply that the same was the general law. 

 Analogy would lead us to believe that the extension of species over the 

 earth originally took place on the same plan on which it is conducted at 

 present, when a new island starts up in the midst of the ocean, produced 

 either by a coral reef or a volcano. In these cases, the whole surface is 

 not at once overspread with plants, but a gradual progress of vegetation 

 is traced from the accidental introduction of a single seed, perhaps, of 

 each species, wafted by winds or floated by currents. The remarkable 

 limitation of certain species to single spots on the globe seems to favour 

 the supposition of specific centres. " 



