TAYLOR : DOMINANCY IN NATURE. 
15 
Geologfy also affords very striking corroboration of the truths of 
geographical distribution and of the intimate connection between the 
community of descent and the chronological sequence of the evolution 
of all animals and plants, inasmuch as the laws governing the suc- 
cession of life in the past are those controlling the evolution of life 
and its distribution over the earth at the present day ; for the 
orderly succession of life presented in the ascending strata of our 
globe could be, in a large measure, reconstructed by a study of the 
plan of the dispersal of life over the various regions of the earth ; 
the chronological sequence of such regions according with their 
remoteness or otherwise from the creative centre ; and this becomes 
most impressive when the survey is from Europe, the location of the 
area of greatest evolutionary activity, and the only possible region 
from which such a survey showing the gradual transition from the 
most modern to the most ancient forms of life can be made, while 
its accordance with geology is demonstrated by the fossilized remains 
imbedded in the most recent deposits being those whose living repre- 
sentatives still exist in or near the European region : while those 
forms of life whose geographical range is restricted to isolated oi' 
desolate spots, or to countries the most remote from Europe, are 
of the greatest geological antiquity. 
The Mollusca,^ the group upon which the preceding generalizations 
are chiefly based, as being my own special study and apparently 
further advanced on this especial line of thought than most other 
groups, will be first considered, and I shall hope to demonstrate 
that their geographical distribution is in strict harmony with the 
serial evolution of the constituent species and genera, and will 
clearly indicate their probable creative centre, and also the routes by 
which they have attained or reached their present area of habitation. 
The HELiciDiE, a characteristic family of land-shells, may be taken 
as a representative group, not only because of their world-wide disper-- 
sal, but because our knowledge of their structure is so complete, that 
a scheme of classification has been based upon it, whose truthfulness 
as revealing natural affinities is shown by the flood of light the 
proposed arrangement sheds on their evolution, their migratory 
paths, and the resulting geographical distribution of the component 
genera, and this is the more remarkable, as previous attempts to 
establish a phylogenetic sequence in harmony with geographical 
distribution have always been chaotic and unconvincing. 
A truly natural classification is, therefore, of indispensable value, 
as revealing the bonds of relationship and establishing the com- 
munity of descent of all life, which is thus shown to be linked 
together by chains of affinities, and although many of the larger 
groups are now broken up and widely separated by immense tracts 
of land or wide oceans, yet each generic type, each ordinal type, and 
even the still larger and more important groups are genetically 
I For a fuller account of distribution, evolution, etc., of the Helicidcr see " Monograph of 
the Land and Freshwater Mollusca of the British Isles," vol. i. 
