Vol. xli.] 142 



distribution and evolution of bird-life, he dwelt on the 

 necessity for intensive collecting and accurate labelling of 

 specimens, as well as a more systematic study of the factors 

 comprised under the headings of topography and climate. 



He then briefly sketched the various life-zones of the 

 Andean chain — Tropical, Subtropical, Temperate, and 

 "Paramo" — illustrating his remarks with a series of beautiful 

 lantern-slides, which formed a fitting background to his 

 remarks upon their characteristic features, their altitudinal 

 limits, their origin, and the development of their several 

 faunas. 



A very interesting and important fact to note in reviewing 

 the Andean faunas was the Zoological " fault " in the sub- 

 tropical zone, between the northern extremity of the Western 

 Andes and the mountains of Western Panama. Here we 

 found that some sixty species, common to the localities just 

 cited, were wanting in the intervening area — a fact which had 

 been considered to indicate subsidence therein. 



From this the attention of members was drawn to a com- 

 parison of the Avifauna of the Temperate Zone forests of the 

 Urubamba region in Southern Peru with that of the adjoining 

 plains of the Paramo or Puna Zone. The first was derived 

 from the tropical forests at the eastern base of the range, the 

 latter from the South Temperate Zone plains of Patagonia 

 and Argentina. Of the genera inhabiting the Temperate 

 Zone forests 55 per cent, were endemic, while only 7 per cent, 

 of the Paramo genera were so. This condition of things 

 might be considered due to the fact that, in ascending from 

 the Tropical to the Temperate Zone forests, birds had 

 experienced far greater environmental change than in 

 passing from the South Temperate Zone of Patagonia to an 

 Andean Temperate Zone ; hence it was believed that the 

 degree of environmental change, expressed primarily in 

 climatic conditions, was a more potent evolutionary factor 

 than those exerted by time, isolation, or distance in space 

 from the original home of the presumed ancestral form. 



