ANNIVEESART ADDRESS OF THE PRESIDENT. 83 



loped groups agree with the present distribution and connexion of 

 land tracts better than those of more ancient origin. The relations 

 between the modern range of ancient families or orders and the 

 ancient distribution of land tracts is a problem which it may be 

 hoped will not always be as difficult as it appears at present. 



Eeviewing the whole evidence, I can only come to one con- 

 clusion, namely, that whilst Sclater"s regions adopted by "Wallace 

 are convenient, and whilst the recognition of them by well- 

 understood names has been of use and has tended to increase our 

 knowledge of geographical distribution, they are, so far as they are 

 natural, a necessary result of the present and later Tertiary distri- 

 bution of land and water, and that they are, to a large extent, 

 artificial, whilst the idea of their equality is an error. The attempt 

 to make all forms of life fit into the particular grooves that were 

 designed to accommodate passerine birds appears to me Procrustean. 



On the whole, the evidence is far too contradictory to be re- 

 ceived as proof of the permanence of oceans and continents. 



So far I have merely laid before you reasons for doubting 

 whether the distribution of animals at the present day agrees so 

 closely with the present arrangement of land and oceanic areas as 

 to lead to the inference that these have always been the same. It 

 is evident that if there are wide distinctions in the distribution of 

 different groups of living beings, all cannot be cited as witnesses 

 to the permanence of continents and oceans in past times. It 

 is quite true, however, that within the continental limits there 

 have existed at various geological periods seas that, even if of no 

 great depth, were just as complete barriers to the migration of par- 

 ticular forms of life as deep oceans would be. The familiar example 

 of the British Islands is sufficient to illustrate this fact. As noticed 

 by Wallace in ' Island Life,' Germany possesses nearly 90 species 

 of land mammals and Scandinavia 60, whilst in Great Britain there 

 are only 40, and in Ireland only 22. Of reptiles and batrachia 22 

 occur in Belgium, 13 in Britain, and only 4 in Ireland. The 

 removal of the isthmus of Suez and the substitution of a shallow 

 inlet, the width of the Straits of Dover, would constitute an impass- 

 able barrier to many animals. 



It remains to be seen whether indications exist of land-connexions 

 in past times across areas now occupied by deep sea. All the dis- 

 cussion hitherto has been to a large extent preliminary to this. 



It must be remembered that diiferent groups of animals vary very 



