28l 



This orderly distribution of life over the whole earth is strong 

 evidence of its origin from a single region, as incongruity and 

 disconnection could hardly fail to be present and recognisable 

 if a varied life was originating and spreading from several 

 independent centres. 



The true direction of these migratory movements, for a 

 behever in Evolution, is also furnished by the acknowledged 

 fact that in all cases, wherever closely investigated, it is found 

 that the most archaic and therefore the earliest evolved species 

 of any group is always in the van, or farthest from the assumed 

 birthplace or centre of dispersal, while the later developed forms 

 are always towards the rear and nearest their place of origin. 



If the species or groups had been evolved in and were spreading 

 from Antarctica, as has been affirmed for various groups of 

 animals and plants, then the earliest evolved should on evolu- 

 tionary principles have spread farthest from their assumed 

 birthplace, while the latest and most perfected forms would not 

 have spread so far : thus its earliest and most modern forms 

 would occupy positions entirely opposite to that of the forms 

 spreading from Palaïarctica, and this is notoriously not the case, 

 and would appear to invalidate the theory of an evolutionary 

 Antarctica. 



In the demonstration of the facts upon which the preceding 

 generalisations are founded, I will commence with my own 

 more especial study, the Mollusca (as it is apparently further 

 advanced on this special line of thought than most other groups), 

 and I shall hope to be able to show you that its geographical 

 distribution is in strict harmony with the serial evolution of its 

 constituent families and genera. 



The Helicidse, upon which the present scheme of distribution 

 is chielly founded, are divided by Prof. Pilsbry into four chief 

 groups — Belogona Siphonadenia, Bclogona Euadenia, Kpiphal- 

 logona, and Protogona, and I have also taken note of a still 

 lowlier and more generali.-:ed group, Haplogoiia. These groups 

 are enumerated in the order of their comparati\e ¡)erfection of 

 structure, beginning with the most highly organised group. 



The Belogona Siphonadenia, to which the typical genus Helix 

 belongs, extend over and are characteristic of the Western 

 Palaearctic region. It is the most advanced group, and its highest 

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