2J.O Recent Literature. L J"lv 



inhabits distinct islands with separating sea channels broad 

 enough to make the passage over difficult and infrequent. 



The above facts make Philippine species and varieties geo- 

 graphical or local groups depending upon local causes for their 

 existence. They show isolation to be the first and the necessary 

 step in the formation of species. 



The foregoing facts make the belief in the fusion of closely 

 allied species, when thrown together, almost necessary. The 

 volcanic character of the islands and the shallow seas separating 

 them, with the observed marks of frequent changes of sea level, 

 make it necessary to believe that the land areas of the Philippines 

 have been continually varying and that, in multitudes of cases, 

 closely allied species have been thrown together by the connec- 

 tion of islands formerly distinct. These closely allied species 

 now no longer existing together, they must have disappeared 

 either by the destruction of one or by their fusion. To one who 

 has observed the likeness in size and coloring and notes and food 

 of these allied forms, the latter is the only reasonable hypothesis 

 for the greater number of cases. 



A satisfactory explanation of many or most of the phenomena 

 of distribution of genera and species in larger and continental 

 areas may be found in giving the same prominence to isolation 

 and fusion in the formation of the species occupying them. 



RECENT LITERATURE. 



Mcllwraith's Birds of Ontario. 1 — The first edition of Mr. Mcllwraith's 

 excellent manual, 'The Birds of Ontario,' published in 1886 (see Auk, IV, 

 18S7, p. 245), was speedily exhausted, so that for some years past the 



1 The I Birds of Ontario | being a concise account of every Species of Bird | known 

 to have been found in Ontario | with a | Description of their Nests ami Eggs | and 

 Instructions for collecting Birds and preparing | and preserving Skins, also Directions 

 how I to form a Collection of Eggs | By Thomas Mcllwraith | Member of the Ameri- 

 can Ornithologists' Union | — | Second Edition — Enlarged and Revised to Date | 

 With Illustrations | — | Toronto | William Briggs, Wesley Buildings | Montreal: 

 C. W. Coates Halifax : S. F. Huestis | MDCCCXCIV— 8vo., pp. i-x, 11-426. 



