NATURAL SELECTION 



systems of classification which arrange species or groups in 

 circles, as well as those which fix a definite number for the 

 divisions of each group. The latter class have been very 

 generally rejected by naturalists, as contrary to nature, 

 notwithstanding the ability with which they have been 

 advocated ; but the circular system of affinities seems to have 

 obtained a deeper hold, many eminent naturalists having to 

 some extent adopted it. We have, however, never been able 

 to find a case in which the circle has been closed by a direct 

 and close affinity. In most cases a palpable analogy has been 

 substituted, in others the affinity is very obscure or altogether 

 doubtful. The complicated branching of the lines of affinities 

 in extensive groups must also afford great facilities for giving 

 a show of probability to any such purely artificial arrange- 

 ments. Their death-blow was given by the admirable paper 

 of the lamented Mr. Strickland, published in the Annals of 

 Natural History, in which he so clearly showed the true 

 synthetical method of discovering the Natural System. 



Geographical Distribution of Organisms 

 If we now consider the geographical distribution of animals 

 and plants upon the earth, we shall find all the facts beautifully 

 in accordance with, and readily explained by, the present 

 hypothesis. A country having species, genera, and whole 

 families peculiar to it, will be the necessary result of its 

 having been isolated for a long period, sufficient for many 

 series of species to have been created on the type of pre- 

 existing ones, which, as well as many of the earlier -formed 

 species, have become extinct, and thus made the groups 

 appear isolated. If in any case the antitype had an extensive 

 range, two or more groups of species might have been formed, 

 each varying from it in a different manner, and thus producing 

 several representative or analogous groups. The Sylviadse of 

 Europe and the Sylvicolidae of North America, the Heliconidae 

 of South America and the Euploeas of the East, the group of 

 Trogons inhabiting Asia and that peculiar to South America, 

 are examples that may be accounted for in this manner. 



Such phenomena as are exhibited by the Galapagos Islands, 

 which contain little groups of plants and animals peculiar to 

 themselves, but most nearly allied to those of South America, 



