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[Pi-oc. 



plants, and pointed out the probable methods of seeds being 

 scattered. Winds, currents, and animals forming, in his opinion, 

 the chief methods of transportation. Nevertheless, he believed 

 that most plants had obtained their present geographical range by 

 means of slow progression over a continuous land surface, rather 

 than by accidental means. He did not consider that whirlwinds 

 and ocean currents had much influenced our island floras. 



Mr. A. W. Stelfox, A.R.I. B.A., said that most of Mr. 

 Praeger's remarks would apply equally to land and fresh-water 

 Shells, and that the habits of these animals appeared to minimise 

 the effects of accidental dispersal. The distribution of the fresh- 

 water species was much more likely to be influenced by changes 

 in watersheds. Thus, a species might penetrate to the source of a 

 river, say a lake, and by means of physical changes this lake might 

 afterwards be captured by a river running in a different direction 

 to that into which the lake had formerly discharged its waters, 

 thereby opening up a new and unoccupied region to the species. 



Mr. F. Balfour Browne, M.A., F.R.S.E., remarked that when 

 Water-beetles had been found on oceanic islands they had 

 evidently been derived from all points of the compass, which 

 pointed to their introduction by accidental means. 



Dr. A. R. Dwerryhouse, F.G.S., thought that Mr. Praeger 

 had minimised the effect of winds as a means of transportation. 

 He pointed out that sand from the Sahara had been known to 

 have been carried to Italy. He agreed with Mr. Stelfox as to 

 the possible influence of changes of watershed affecting the 

 distribution of a fresh-water fauna, and pointed out that such 

 physical changes were constantly happening at the present day. 



Professor Gwynne-Vaughan, M.A., agreed with the two last 

 speakers, and considered that accidental dispersal was quite 

 sufficient to account for the present distribution of our flora. 



Mr. N. H. Foster said that it appeared that the present 

 distribution of some of the invertebrate groups could not be 

 accounted for otherwise than by means of former land connections. 



