308 Notes on the Indian terrestrial Gasteropoda. [ No. 4, 
gin of Species,—the unlimited application of facts which have but a 
limited bearing. It is as though any one should argue, that because 
aman may live to 20 years or 40 or 80, therefore he may live 
to 160. Migration of species as well as individual changes may take 
place, but to these there are limits not the less impassable, because 
not sharply defined. Many of our domestic animals are as artificial 
creations as our 8-day clock, but their variation from the focal stocix, 
though censiderable, and ill-defined in its limits, is subject to certain 
bounds; and I cannot see that from these known deviations, it is 
logical to argue unknown deviations, such as no sick man ever dream- 
edof: or that a bear, though the breeder might in time lengthen his 
nose or shorten his claws or fur, could ever suffer a sea change and 
cleave the deep like a whale, any more than he could scale the heavens 
like a cherub. The idea may be philosophical but it zs absurd. 
Those who reject the idea of original or archetypal pairs of all 
animals in favour of the theory of “natural selection,’ must embrace 
the same views regarding the method of their distribution, as those 
who hold every animal to have radiated from Mt. Ararat, as lineal 
descent is the Ariadnean thread whereby they seek to solve the 
mystery of the “ parsley bed,” but though this theory certainly shifts 
the difficulty a long way off, yet it by no means disposes altogether 
of the necessity of a primordial ‘‘ blue bag” of some sort or another, 
as none of its adherents, that I am aware of, have advanced any 
refutation of the accepted aphorism. 
“ sion 
“ F nihilo nihil, in nihilem nil posse reverti.” 
It is clearly essential for those who support the natural selection 
theory, and regard species as merely pronounced or rigorous varieties 
springing from the same stock, to establish the efficacy of transport 
or migration, to bring about the distribution of all animals within 
their respective areas : hence the variety of means suggested for that 
end, most of which seem, to say the least of it, far fetched and impro- 
bable. Earth, ocean, and the winds of Heaven are taxed in turn to 
afford means of transport for widely diffused species ; hence the inter- 
est attaching to a careful study of the distribution of the mollusca, 
as affording serious grounds for doubting some of the conclusions the 
above theory necessitates, and the light which it is likely to afford to 
future enquirers. But to return to the more immediate subject of re- 
mark :—the diffusion of terrestrial mollusea over their individual area 
