5 THE DEPTHS OF THE SEA. [CHAP. I. 
Forbes defined and advocated what he called the 
law of representation. He found that in all parts 
of the world, however far removed, and however 
completely separated by natural barriers, where the 
conditions of life are similar, species and groups 
of species. occur which, although not identical, 
resemble one another very closely; and he found 
that this similarity existed likewise between groups 
of fossil remains, and between groups of fossils 
and groups of recent forms. Admitting the con- 
stancy of specific characters, these resemblances 
could not be accounted for by community of de- 
scent, and he thus arrived at the generalization, 
that in localities placed under similar circumstances, 
similar though specifically distinct specific forms 
were created. These he regarded as mutually repre- 
sentative species. 
Our acceptance of the doctrines of specific centres 
and of representation, or, at all events, the form in 
which we may be inclined to accept these, depends 
greatly upon the acceptance or rejection of the funda- 
mental dogma of the immutability of species; and 
on this point there has been a very great change of 
opinion within the last ten or twelve years, a change 
certainly due to the remarkable ability and candour 
with which the question has been discussed by Mr. 
Darwin’ and Myr. Wallace,’ and to the genius of Pro- 
1 The Origin of Species by means of Natural Selection ; or, the 
Preservation of Favoured Races in the Struggle for Life. By Charles 
Darwin, M.A, F.R.S., L.S., G.S., &. &e. London, 1859, and subse- 
quent editions. 
2 Contributions to the Theory of Natural Selection. A Series of 
Essays by Alfred Russel Wallace. London, 1870. 
