lt of sea is
not by any means an insuperable barrier; whereas in reptiles and
amphibians, on the contrary, we have always been weak, seeing that most
reptiles are bad swimmers, and very few can rival the late lamented
Captain Webb in his feat of crossing the Channel, as Leander and Lord
Byron did the Hellespont.

Only one good-sized animal, so far as known, is now peculiar to the
British Isles, and that is our familiar friend the red grouse of the
Scotch moors. I doubt, however, whether even he is really indigenous in
the strictest sense of the word: that is to say, whether he was evolved
in and for these islands exclusively, as the moa and the apteryx were
evolved for New Zealand, and the extinct dodo for Mauritius alone. It is
far more probable that the red grouse is the original variety of the
willow grouse of Scandinavia, which has retained throughout the year its
old plumage, while its more northern cousins among the fiords and fjelds
have taken, under stress of weather, to donning a complete white dress
in winter, and a grey or speckled tourist suit for the summer season.

Even since the insulation of Britain a great many new plants and
animals have been added to our population, both by human design and in
several other casual fashions. The fallow deer is said to have been
introduced by the Romans, and domesticated ever since in the successive
parks of Celt and Saxon, Dane and Norman. The edible snail, still
scattered thinly over our southern downs, and abundant at Box Hill and a
few other spots in Surrey or Sussex, was brought over, they tell us, by
the same luxurious Italian epicures, and is even now confined,
imaginative naturalists declare, to the immediate neighbourhood of Roman
stations. The mediaeval monks, in like manner, introduced the carp for
their Friday dinners. One of our commonest river mussels at the present
day did not exist in England at all a century ago, but was ferried
hither from the Volga, clinging to the bottoms of vessels from the Black
Sea, and has now spread itself through all our brooks and streams to the
very heart and centre of England. Thus, from day to day, as in society
at large, new introductions constantly take place, and old friends die
out for ever. The brown rat replaces the old English black rat; strange
weeds kill off the weeds of ancient days; fresh flies and grubs and
beetles crop up, and disturb the primitive entomological balance. The
bustard is gone from Salisbury Plai