THE GLACIAL RANGE CONTRACTION, ETC. 75 



tribution is continuous throughout the area, and has 

 probably always been so during the entire period over 

 which our present investigation extends, their range 

 contracting southwards by extermination and expand- 

 ing northwards by colonization contemporaneous with, 

 and in obedience to, the changes of climate. The fol- 

 lowing table will serve readily to demonstrate these 

 interesting; facts. 



CANARY ISL. 



1 Resident in B.ilearic Islands, Corsica, Sardinia, Italy, and Sicily. 



" Recorded by Mr. Scott Elliot from an elevation of 10,000 feet (Mt. " Ruwenzori") 

 near the Albert Edward Nyanza (conf. Nature, 1895, p. 271). 



3 This species now only reaches the Canary Islands, the extreme southern portion of 

 its refuge area in Western Europe, as a winter visitor in varying numbers, having ceased 

 to breed therein. 



