382 Biographical Notice of Edward Forbes. 
Mr. Horner, when President of this Society, has borne his 
ready testimony to the merits of this work, when he says in his 
Anniversary Address in 1847, that this Essay “is an admirable 
example of the light to be derived from other branches of natural 
history in the prosecution of geological inquiries ; of the applica- 
tion of animal and vegetable physiology, and a knowledge of the 
habits and distribution of animals and plants to the elucidation of 
very difficult problems in geology.”’ Mr. Horner, in the Address 
as it is of great and enlightened views. I will therefore here 
only observe, that the principal theory which it is the object of 
this Essay to establish, is based on the assumption of the exist- 
ence of specific centres, that is, of certain geographical points from 
which the individuals of each species have been diffused, involv- 
ing their consequent descent from a single progenitor, or from two, 
according as the sexes might be united or distinct. Prof. Forbes 
further declares, as his opinion, that the “abandonment of this 
doctrine would place in a very dubious position all evidence the 
paleontologist could offer to the geologist, towards the comparison 
and identification of strata, and the determination of the epoch of 
their formation.” Having assumed the truth of the doctrine of 
specific centres, the problem which he proposes to solve is the 
origin of the assemblages of the animals and plants now iuhabit- 
ing the British Islands. Within this limited area he considers 
that the united labors of British naturalists have shown that there 
are a great number of animals and plants which are not univer- 
sally dispersed, but are congregated in such a way as to form dis- 
tinct regions or provinces. ‘The vegetation, for instance, presents 
five well-marked Floras, four of which are restricted to definite 
provinces, whilst the fifth, besides exclusively claiming a part of 
the area, overspreads and commingles with all the others. 
Prof. Forbes considers that, of the three given modes by which 
an isolated area may become peopled by animals and plants, “ im- 
migration before isolation” of the area was the mode by which 
the British Isles have chiefly acquired their existing flora and 
fauna, terrestrial as well as marine, and that it took place subse- 
quently to the Miocene epoch. It follows from this argument, 
that previous to the isolation of this area, it must have been in 
direct union with those portions of the European continent the 
floras of which are shown to be identical with one or other of the 
five floras of the British Isles. I will briefly mention the five 
distinct floras which he has noticed, and the districts with which 
he considers they prove our former connexion. 
1. The West Irish Flora.—The high lands in the North of 
Spain present the nearest point where a vegetation occurs iden 
tical with that which is characteristic of the mountainous district 
