ANNIVERSARY ADDRESS OF THE PRESIDENT. 77 



to the fauna of the Trias, he said, " It does not appear to me that 

 there is any necessary relation between the fauna of a given land 

 and that of the seas of its shores. At present our knowledge of the 

 terrestrial faunaB of past epochs is so slight that no practical difficulty 

 arises from using, as we do, sea-reckoning for land-time. But I 

 think it highly probable that, sooner or later, the inhabitants of the 

 land will be found to have a history of their own." 



The growth of our knowledge concerniug the terrestrial floras and 

 faunas of aucient geological periods, since these words were written 

 in 18G9, has constantly forced upon the minds of many geologists 

 the necessity of a duplicate classification of geological periods, 

 based on the study of marine and terrestrial organisms respectively. 



Upon this important question the judicious remarks of my col- 

 league Dr. Blanford must still be fresh in the minds of all geologists 

 and biologists. He showed that not only are terrestrial provinces 

 independent of marine ones, but that at present, as well as in the 

 past, the former are more circumscribed and have an amount of 

 distinctness which does not exist in the case of the latter. 



Nor is it difficult, in the present state of our biological knowledge, 

 to give a reason for the existence of this state of things. Between 

 completely separated land- areas, migration can only take place by 

 such accidents as the transport of seeds or eggs, or as the con- 

 sequence of the great but slow changes in the relations of sea and 

 land. Porms adapted only for living in cold climates are isolated 

 by tracts of low-lying tropical land, and, conversely, tropical forms 

 are divided off from one another by snow-covered mountain-chains, 

 almost as distinctly as by actual oceans. The fact that well-known 

 arctic plants are found at the top of mountains in tropical or tem- 

 perate lands has seemed to many botanists to be quite inexplicable 

 without calling in the agency of a general refrigeration, like that 

 which is supposed to have marked the glacial period. 



But with marine forms of life the case is totally different. The 

 oceans are not only much larger than the continents, but they are 

 all more or less comjjletely connected with one another ; and this 

 more or less complete connexion of the oceanic areas must have 

 been maintained from the earliest geological times. 



Eorms which live at the surface of the ocean may wander freely 

 in all directions, and know but few limitations except those imposed 

 by temperature, absence of food, «&c. ; forms which characterize 

 moderate depths may migrate along shore-lines or submarine ridges 

 from one area to another ; and even when abysmal tracts of ocean 



