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PEOF. J. LOGAN LOBLEY, F.G.S., F.R.G.S., ON 



supply more food to several insects, and probably to some 

 terrestrial testacea, so that the latter would gain ground. The 

 increase of these would furnish other insects and birds with 

 food, so that, the numbers of these last would be augmented. 

 The diminution of the seals would afford a respite to some fish 

 which they had persecuted ; and these fish, in their turn, would 

 then multiply and press upon their peculiar prey. Many water- 

 fowls, the eggs and young of which are devoured by foxes, 

 would increase when the foxes were thinned down by the 

 bears ; and the fish on which the water-fowls subsisted would 

 then, in their turn, be less numerous. Thus the numerical 

 proportions of a great number of the inhabitants, both of the 

 land and sea, might be permanently altered by the settling of 

 one new species in the region ; and the changes caused 

 indirectly would ramify through all classes of the living 

 creation, and be almost endless." 



When it is found that extensive areas have been elevated 

 14,000 feet since Pliocene times, for in the Himalayas deposits 

 of that age are now 14,000 feet above sea level, we must be 

 impressed with the magnitude and vast number of geographical 

 alterations that have taken place throughout geological time, and 

 also with the almost infinite number of consequent possibilities 

 that would affect, in one way or another, animal and vegetable 

 life on the globe, and so be productive of biological change. The 

 exact conditions of each period of geological time, and of each sea, 

 and bay. and estuary, and lake, existing in each of these periods, 

 or each of the many and constantly varying land conditions of 

 elevation, exposure, temperature, and humidity, we cannot 

 hope to know, and so we cannot hope to be able to give the 

 specific causes of specific changes, but the general cause of 

 biological change does not appear so inexplicable. 



" The fact of heredity is recognised," Dr. Saleeby says, by 

 every man who would show surprise on hearing that an acorn 

 had developed into a human being or a mushroom," and " the 

 man in the street need not leave the street in order to find 

 conclusive evidence of the fact of variation."* But it is also 

 necessary to remember that " tlie link which unites all organ- 

 isms is not always the common bond of heritage, but the 

 uniformity of organic laws acting under uniform conditions."! 



* Fortnightly Review, 1905, p. 604. 



t G. H. Lewes, Fortnightly Review, 18G8, p. 373. 



