The distribution of the British plants has been worked out much more thoroughly than that of the animals. It need not surprise us, therefore, that the first attempt to separate the British Islands into natural divisions was made by a botanist--the late Mr. Watson. As he himself pointed out, in making these divisions he did not take into consideration the origin of the British species. They represent merely groups of assemblages of plants of different types of vegetation. Edward Forbes, on the other hand, founded his districts on the origin of plants. His work is not only the first of the kind, but it is a classical essay, and remains one of the most remarkable contributions to the literature on the geographical distribution of living organisms known to science. The vegetation of the British Islands, he informs us (p. 4), presents a union of five well-marked floras, four of which are restricted to definite provinces, whilst the fifth, besides exclusively claiming a great part of the area, overspreads and commingles with all the others. These are-- I. Mountainous districts of South-west } and West of Ireland. } Lusitanian type. II. South-west of England, and } South-east of Ireland. } Gallican type. III. South-east of England. IV. Mountains of Scotland, Cumberland, } and Wales. } Scandinavian type. V. General Flora. Germanic type. Professor Forbes points out, in connection with the plants of the Germanic type, that the fauna accompanying this flora presents the same peculiarities and diminishes westward and to the north. This type includes, therefore, almost all the species which can be shown to have come to us directly from the east, few if any of which have penetrated to Ireland. On a previous occasion, the same author had divided the British Islands into ten districts, according to the distribution of their molluscan fauna. These are-- I. The Channel Isles. II. South-east of England (including Cambridgeshire). III. South-west of England. IV. North-east of England. V. North-west of England (including Isle of Man). VI. North of Ireland. VII. South of Ireland. VIII. South of Scotland. IX. North of Scotland. X. Shetland Isles. In a short paper on this subject (_b_, p. 5), I have shown that some of these districts are founded on erroneous data, whilst, with the knowledge now at our disposal, others can no longer be maintained as distinct. I thought then that the molluscan fauna warranted a division of the British Islands into the following two provinces:-- I. England and Wales (except the South-west). II. South-west of England and Wales and the whole of Ireland and Scotland.