[[p. 58]] Mr. Wallace, in the first place, called attention to the fact, now well established, that all large islands which have been separated for a long period of time from the mainland, possess species of animals and plants which are peculiar to them, the number of peculiar species, speaking generally, being large or small, according to the length of time during which the island has been cut off from the land of which it formerly formed part. He also pointed out that these are very significant facts in connection with the geographical distribution of animals and plants. He further stated that his researches having led him to the conclusion that the British islands, although they had only been separated from the continent in comparatively recent times, were no exception to this rule, he applied to a number of distinguished men who had made special studies of various departments of zoology and botany, but they one and all gave it as their opinion that there were no animals or plants which were peculiar to Great Britain, and that probably every species to be found in our islands would be found on the continent if proper and sufficient search were made for it. Not being satisfied with these replies, he proceeded with his investigation, which resulted in his coming to the conclusion that there are a considerable number of species recorded as occurring in Great Britain which are not to be found in any other part of the world.

     Mr. Wallace went on to show that there is much direct and positive evidence that the British islands once formed part of the continent of Europe, and were formerly more extensive than they now are, also that their connection with the continent has been broken and again re-established more than once, and he went through this evidence in detail.

     He next proceeded to show that the number of species of animals and plants which occur on the continent of Europe is much larger than the number which is to be found in Great Britain, and these again, in their turn, are considerably larger than the number of species which have been recorded as occurring in Ireland, whilst Ireland again has species which are not to be found in Great Britain. All this seemed to show that Ireland was separated, as an island, from Great Britain some time before Great Britain ceased to form part of the European continent. With regard to the species peculiar to the British islands, it is probable that they have all come into existence since the islands were last severed from the continent, and the fact that [[p. 59]] this severance took place in comparatively recent times would account for the comparatively small number of species which are peculiarly British.

     Taking the animal kingdom in detail, Mr. Wallace shewed that, in the opinion of the best authorities, our islands have no peculiar species of Mammalia or Reptiles, but of birds there are three species, the Red Grouse (L. scoticus) the English Coal Titmouse (P. britannicus) and the British Long Tailed Titmouse (A. rosea), which do not occur elsewhere. Of fishes there are fifteen species, all of freshwater fish, which are not to be found on the continent; six of these are peculiar to Ireland, two of them to be found only in one lake. Of the British Trout, two species are peculiar to the Orkneys, one to the lakes of Dumfries (which are little more than moderate-sized fish ponds connected with Dumfries Castle), one to Wales, two to the English lakes, and three to the Scotch lakes. The difference between these species is not in colour only, but in structure, and the favourable conditions under which they have probably been developed was explained in detail by Mr. Wallace.

     Passing to invertebrate animals, Mr. Wallace pointed out that insects, being smaller in size, and therefore more easily overlooked, were more difficult to deal with; but there is every reason to believe that there are many species of insects which occur only in the British isles. The English climate, from its mildness in winter, and other peculiarities, is favourable not only to the production of new species, but also to the survival of others, which are not able to endure the winter of many parts of the continent. Among the Lepidoptera there are over one hundred species, which have been found in our islands, but which are not known to occur on the continent. After making every allowance there are probably seventy of these species which are really peculiar to Great Britain and Ireland. Of these seventy species there are only unique specimens of some, others are very rare, and others rather common. Two of the unique specimens were taken at Sanderstead, near Croydon, one in 1848 and the other in 1854. Mr. Wallace exhibited a case of Butterflies and Moths, lent to him by Mr. Charles Stevens, containing, amongst others, the large Copper Butterfly (P. hippothoe), formerly abundant in some parts of Great Britain, but believed now to be extinct, and pointed out in it and described some of the unique specimens to which he had referred. He also exhibited a case of Butterflies and Moths taken in the Isle of Man, and with them a series of the specimens most nearly resembling them which are to be found in the other British islands, and the peculiarities of each were pointed out and described. Of Coleoptera about seventy-two species, and of Trichoptera three species are peculiar to [[p. 60]] Britain. The little island of Lundy, in the Bristol channel, has two insects, one a distinct species, the other a variety only, which are peculiar to it, and other restricted areas have species and varieties of insects which are peculiar to them. Of Mollusca four species only, one of them considered doubtful, are peculiar to Britain.

     Of plants, Mr. Wallace enumerated two Flowering Plants, sixteen Mosses, and ten Hepaticæ, which are peculiarly British.

     Of the two flowering plants, one Brewers' Spotted Rock Rose (H. Breweri), is peculiar to Anglesea and Holyhead island; the other, a water Dropwort (O. fluviatilis), an umbelliferous plant, is found nowhere but in the southern half of England and in one locality in Ireland. Great Britain also possesses two plants, both truly indigenous, which must have come to it from North America, as they are not to be found anywhere except in North America and the British isles. These are a small orchid (Spiranthes romanzoviana) which occurs in Ireland, and the Pipewort, (Eriocaulon septangulare) which is found in the Hebrides and in Ireland. There is no reason at all to believe that these species have been artificially introduced, and it is difficult to understand how they could have been transported to our shores. Ireland also possesses about twenty species of Flowering Plants which are not to be found in Great Britain. Many of these are known to occur in the south of Europe, and two of them are Arctic or Alpine plants. Of the British Mosses and Hepaticæ, three genera of each are not found in any other part of Europe, but occur in various parts of South America, and of Africa and Asia, and in the mountains of New Zealand. Probably these plants, and the twenty species which are peculiar to Ireland are the remains of forms, which, in the remote past, were spread over the greater part of the globe, and which have been enabled to survive in Ireland or Great Britain, by the exceptionally mild climate.

     In conclusion, Mr. Wallace pointed out that, as has been shown by Mr. Darwin, the rarity of a species is one great proof that it is undergoing the process of extinction. Species are now, and always have been, liable to extinction by their enemies becoming too strong, or the conditions of life too severe, and hence it happens, that in islands where the enemies are less numerous, and the conditions more equal, the race is continued, and allowed to survive; and this fact should stimulate and encourage naturalists to make a more thorough and exhaustive investigation of the animals and plants which occur in the numerous islands which surround our coast. There is yet a great deal to be ascertained with regard to them, and no doubt new species yet to be discovered.