1913-1914.] 



47 



the relationship of the fauna we ought to know something of its 

 origin and the causes which facilitated the entry of animals into 

 Ireland. 



The most important factor that we have to consider in this 

 connection is the problem of a possible recent land-connection 

 between Ireland and Great Britain. It seemed to me appropriate, 

 therefore, to submit to your notice in the first instance a few 

 zoological facts which most clearly denote that Ireland has under- 

 gone striking changes in the level of land and water during recent 

 geological times. 



Although the problems of earth movements, strictly speaking, 

 appertain to the domain of Geology, faunistic studies have often 

 rendered most valuable services to the sister Science in their 

 elucidation. Indeed, whenever attempts have been made to 

 investigate whether an island ever had any land-connection with a 

 neighbouring Continent, geologists have readily availed themselves 

 of the data furnished by faunistic studies. Not alone faunistic 

 researches : every new fact of plant and animal distribution in 

 Ireland aids our enquiries into the geological history of the 

 country in some measure. 



The zoological facts referred to, which most clearly denote 

 that Ireland has undergone striking changes in the level of land 

 and water in recent geological times, are founded on the geo- 

 graphical distribution of animals. To anyone who has read 

 Wallace's works the term "geographical distribution of animals" 

 must be most familiar. But possibly some of you may not be 

 acquainted with these works. I may be excused, therefore, for 

 mentioning that the area inhabited by any given kind of animal 

 is called its geographical distribution. 



There are many kinds of animals whose geographical dis- 

 tribution extends all over the British Isles, that is to say, they 

 occur in Great Britain as well as in Ireland. Among these animals 

 there are some which certainly do not now-a-days cross the Irish 

 Channel. How is it then that they succeeded formerly in 



