t--they have come
to greater Europe from that direction.

In discussing the component elements of the British fauna and flora in
the third chapter, I have already referred to the distinguishing
characters of the Lusitanian migrants and to their distribution. I need
only repeat, therefore, that these are now principally confined to the
south-western portions of the British Islands. The late Edward Forbes
was the first to trace the Lusitanian flora to its native home. In his
classical memoir on the geological relations of the existing fauna and
flora of the British Isles, he laid the foundations of a new method of
research. We are as yet only beginning to realise the far-reaching
conclusions obtainable by a careful study of the geographical
distribution of animals and plants, though the lines of investigation
were indicated by him more than fifty years ago. Forbes was of opinion
that the Lusitanian element in the British flora was of miocene age, and
that it survived the Glacial period on a now sunken land to the
south-west of Ireland. Mr. Carpenter and myself agree in so far that we
are both inclined to look upon this Lusitanian flora and the
accompanying fauna in Ireland as of pre-glacial origin. But I am not
quite satisfied that the Lusitanian migration ceased to come north then.
It may have received a temporary check; but the presence, for instance,
of the Dartford Warbler (_Melizophilus undatus_) in the south-east of
England would seem to indicate that its northward migration took place
in very recent times. It is possible also that the very restricted
occurrence of the Dartford Warbler may imply that it is gradually
withdrawing towards its centre of origin from a former wider range. Such
an eventuality, as we have seen, has actually taken place in a great
number of instances.

It is not only in the British Islands that we perceive the influence of
the Lusitanian element. Scandinavia, Russia--indeed almost every part of
Europe--can boast of some migrants which have originated in
South-western Europe or on the mysterious lands which lay beyond it. As
a rule, however, we notice a marked decrease of Lusitanian species as we
travel eastward from Western Europe. Nevertheless, certain forms have
travelled far beyond the confines of our continent, and we certainly
meet with them in Asia and Northern Africa.

It is remarkable that we are apt to mistake sometimes for Lusitanian
migrants species which are of Oriental origin