306 
Darwinism,” refers to the pulmo-gasteropoda of Madeira. He 
says :—‘ It is seen that in isolated islands and island groups these 
earth-bound animals, migrating with so much difficulty have 
attained an extraordinary diversity. In the Madeira Islands, 
134 species of pulmo-gasteropoda were reckoned to exist, of 
which only 21 were to be found in the Africo-European fauna. 
These and the 113 other species are mostly confined to narrow 
districts and single valleys. . . . We must infer that a con- 
nection at one time existed between Europe and Madeira, and. 
that these 21 species remained what they were before the separa- 
tion, while from unknown species still appearing in analogous 
forms upon the continent emanated the remarkable profusion of 
new species. They and their comrades on other isolated islands 
were spared a conflict many sided, and they doubtless afford a 
favourable example of Wagner’s law of migration, as with the ~ 
difficulties of locomotion and the improbability of a large subse- 
quent arrival, the secluded individuals under even slightly different 
influences, had had a prospect of diverging from the parent 
species.” The Rev. Mr. Gulick in writing on the Hawaian Land 
Snails, as the result of 15 years study, also refers to the effects of 
isolation in producing a very large number of species. For this. 
production of diversity we must assume in the respective genera 
a large amount of plasticity or power of accommodation to environ- 
ment, and to a comparatively late appearance in biological evolu- 
tion. If such an old mollusc as trigonia is taken we find a won- 
derful absence of plasticity, and a marked contrast to what has 
been said of certain island pulmo-gasteropoda, for it is solely now 
found living in Australian waters, being represented by six 
species only, vide W. T. Bednall, vol. I., Trans. Roy. Soc., S.A. 
The same writer says this ‘‘ genus was excessively rich in repre- 
sentatives from its advent at the beginning to the close of the 
Secondary Age in Europe, when it died out altegether ; whereas. 
in Australia it has survived throughout the whole period of 
Secondary and Tertiary times until the present day, though it 
must be admitted in a very limited degree in regard to number.” 
It has already been referred to as forming one of the Australia- 
like features of the Stonefield Slate. We see, therefore, on the 
one hand certain molluscs diverging into numerous species ; and 
on the other hand a mollusc restricted to six species only and to- 
one continent. Applying this to the Australian aboriginal, we 
infer that he does not possess plasticity, and has only been handed 
down from a most remote antiquity by propitious and protective 
isolation. 
The conclusion then is that the Australian is not degenerate 
but primordial, and that this is shown by his still absolutely 
identifying himself with other natural objects around him; and 
