Presidential Address. 2*79 



of wide distribution are exceptionally great for marine 

 species, this is not so. Except in the case of those which 

 enjoy a period of free locomotion when young, or are floating 

 and pelagic, the deep ocean sets bounds to their migrations. 

 On the other hand, the spores of cryptogamic plants may be 

 carried for vast distances by the wind, and the growth of 

 volcanic islands may affect connections which, though only 

 temporary, may afford opportunity for land animals and 

 plants to pass over. 



With reference to the transmission of living beings across 

 the Atlantic, we have before us the remarkable fact that from 

 the Cambrian age onwards there were, on the two sides of 

 the ocean, many species of invertebrate animals which, were 

 either identical or so closely allied as to be possibly varietal 

 forms. 1 In like manner, the early plants of the Upper 

 Silurian, Devonian, and Carboniferous, present many identi- 

 cal species, but this identity becomes less marked in the ve- 

 getation of the more modern times. Even in the latter, how- 

 ever, there are remarkable connections between the floras 

 of oceanic islands and the continents. Thus the Bermudas, 

 altogether recent islands, have been stocked by the agency 

 chiefly of the ocean currents and of birds, with nearly 150 

 species of continental plants, and the facts collected by 

 Helmsley as to the present facilities of transmission, along 

 with the evidence afforded by older oceanic islands which 

 have been receiving animal and vegetable colonists for 

 longer periods, go far to sbow that, time being given, the 

 sea actually affords facilities for the migration of the in- 

 habitants of the land, comparable with those of continuous 

 continents. 



In so far as plants are concerned, it is to be observed that 

 the early forests were largely composed of cryptogamous 

 plants, and the spores of these in modern times have proved 



1 See Davidson's Monographs on Brachiopods ; Etheridge, Address 

 to Geological Society of London; Woodward, Address to Geologists' 

 Association; also Bar rande's Special Memoirs on the Brachiopods, C'eplia- 

 lapods, &c.,: and Hall, Palaeontology of New York; Billings, Reports, 

 on Canadian Fossils ; and Matthews, Cambrian of Neiv BrunsioicP, 

 Trans. R. S. C. 



