1885.] 
Acclimatisation. 
209 
them very strongly. Surely a grim satire on the “ survival 
of the fittest ! Whatsoever we would wish to destroy 
survives, sets us at defiance, and spreads round.the globe 
like a pestilence. Whatsoever we wish to preserve taxes 
our constant efforts, is often in danger of extirpation, and 
rarely very rarely indeed — succeeds in spreading sponta- 
neously into new regions. It is easy to enumerate beautiful 
plants, such as the lily of the valley and certain of the 
choicer ferns, which are assuredly disappearing from the 
British flora. 
In like manner the roller, the oriole, and the bee-eater 
have vanished from our fauna, and the kingfisher is surely 
following them. We need, therefore, scarcely ask why 
such species do not attend the footsteps of our colonising 
pioneers ? 
It may be said that lovely flowers, birds, and inserts are 
extii pated on account of their beauty. A careful examina- 
tion will show that this is not the fundamental fadt. Lilies 
of the valley in our woods and field-edges are carried off 
foi sale wherever seen. But what a far wider devastation 
falls to the lot (say) of the groundsel, the thistle, the dock, 
&c. Every gardener, from the extensive nurseryman to the 
humblest amateur, massacres these plants by thousands. 
So does every farmer. They have also other enemies. 
I heir seeds are the food of birds ; their leaves are attacked 
by caterpillars, and their flowers and buds by Aphides. But 
are they decreasing ? We may congratulate ourselves if 
we can keep them from gaining further ground. 
It is surely a difficult problem to say why and how tena- 
city and the power of multiplication are thus, apparently at 
least, preferentially linked with ugliness and harmfulness. 
But, admitting the bare fadt, we need not wonder why the 
plants and animals which we admire should so rarely become 
accidentally acclimatised. 
I he main peril of naturalising any species lies in the cir- 
cumstance that we can rarely judge how its habits and its 
powers may be modified by novel surroundings. We know 
now that the diet and the rate of increase of an animal are 
not points immutably fixed, but are open to change. If a 
destructive insedt is conveyed to a climate where the sum- 
mer is longer and more decided, it may produce an additional 
brood of descendants every season. A still more frequent 
case is that in its original home it may have been kept in 
check by some parasite or other destroyer. But when trans- 
ferred to another hemisphere these enemies may not have 
accompanied it. Hence its increase is, for a time at least, 
