The introduction by man of various species of plants and animals into a region where they formerly did not exist has in some cases pro foundly changed the native fauna and flora. A single well-authenticated illustration will suffice, though many more could be adduced. The is land of Saint Helena was discovered about the year 1506, and at that time was densely cov ered with forests. In a little more than 300 years, fully five-sixths of the island had become entirely barren, and, as reported by Dr. Hooker, most of the existing vegetation was not indige nous but consisted of plants introduced from Europe, Africa, America and Australia. These exotic species, together with the goats, were carried to the island through the agency of man.
The goats destroyed the forests by eating the young plants, and the native vegetation could not compete in the struggle with the introduced species. It is estimated that 100 peculiar and indigenous species were extirpated in this man ner, and all record of them is lost except a few species preserved in the Kew herbarium.
Besides the species already exterminated by man, it should be noted that many others were once abundant and widespread that are now re duced in numbers and restricted in range. Their final extinction seems to be a matter of a few years only. Among these may be mentioned the American buffalo, the fur-seal, the beaver, the elephant and the big-tree of California.
The violent catastrophes of nature seldom affect more than a very limited area of the globe, and species that are cosmopolitan or of wide geographic distribution would not be in danger of extermination. When, however, it is realized that some species are so restricted in their province as to occupy a single valley or a small island, then it is easy to believe that at rare intervals some great and sudden up heaval, subsidence, hurricane or volcanic out break may have destroyed all the individuals of certain localized species, if any such were within the area of disturbance. A West Indian hurri
cane in 1898 is believed to have totally destroyed a species of humming-bird peculiar to the is land of Saint Vincent, though it is doubtful whether the great eruption of Krakatoa in 1883 and of Mont Pelee in 1902 exterminated a single species of animal or plant.
A review of the various causes of extermina tion shows that on account of their diversity and often extremely slow action it is difficult in any particular case to explain the total disap pearance of a species unless a detailed knowl edge can be obtained of the principal agencies affecting in any way the harmony of its sur roundings or its ability to maintain its numbers in its natural province.
Bailey,