ANNIVERSARY ADDRESS OF THE PRESIDENT. Iv 



The Pleistocene {Newer Pliocene^ Period, 



The Essay of Professor Edward Forbes in the first volume of the 

 Memoirs of the Geological Survey of Great Britain, " On the con- 

 nexion between the distribution of the existing Fauna and Flora of 

 the British Isles, and the Geological Changes which have affected 

 their area, especially during the epoch of the Northern Drift," is an 

 admirable example of the light to be derived from other branches 

 of natural history in the prosecution of geological inquiries, of 

 the application of animal and vegetable physiology, and a know- 

 ledge of the habits and distribution of animals and plants, to the 

 elucidation of very difficult problems in Geology. The memoir is 

 so interesting and attractive throughout, so suggestive of great views, 

 that 1 am tempted to dwell upon it at some length. 



The principal theory which it is the object of this essay to establish 

 is based on the assumption of the existence of specific centres^ that 

 is, of certain geographical points from which the individuals of each 

 species have been diffused ; and their consequent descent from a 

 single progenitor, or from two, according as the sexes might be 

 united or distinct. The author further declares, as his opinion, 

 that " the abandonment of this doctrine would place in a very 

 dubious position all evidence the palaeontologist could offer to the 

 geologist, towards the comparison and identification of strata, and 

 the determination of the epoch of their formation." Having as- 

 sumed the doctrine of specific centres as true, the problem he pro- 

 poses to solve is, the origin of the assemblages of the animals and 

 plants noiv inhabiting the British Islands. The enumeration of the 

 species and the distribution of our indigenous animals and plants, 

 according to our author, have been vt^orked out by the united la- 

 bours of many British naturalists, more completely perhaps than 

 those of any other country ; but he considers that the history of their 

 respective birth-places or origin is still to be made out. Within the 

 limited area of the British Isles, there are a great number of animals 

 and plants which are not universally dispersed, but are congregated 

 in such a way as to form distinct regions or provinces, which have 

 remained unchanged as long as there are any records. The vegeta- 

 tion 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. 



The author is of opinion that there are only three modes in which 

 an isolated area may become peopled by animals and plants : 1st, by 

 special creation within that area ; and there is every reason to believe 

 that that mode had but little influence in determining the vegetation 

 and animal population of the British Isles : 2ndly, by transport to it ; 

 and for many reasons he considers that to be an insufficient mode ; 

 and Srdly, by migration before the isolation of the area ; and this last 

 he believes to have been the mode by which the British Isles have 

 chiefly acquired their existing flora and fauna, terrestrial and marine, 

 and that it took place subsequently to the Miocene epoch. I shall 

 first shortly describe the Five Floras. 



