A.20 Recent Literature. [October 



portion is the part eliminated by the eniargination of the vane. To give 

 the portion of the vane thus cut away sufficient strength and breadth to 

 add its share to the sustaining power of the wing, the vane would have to 

 be thickened to make it more rigid, and broadened to fill the wide interval 

 between the tips of the feathers, thus making a heavy club-shaped clumsy 

 tip to the feather, and obviously decreasing the efficiency of tlie wing as 

 an organ of flight. 



" Further evidence of the pertinency of this explanation ol" eniargina- 

 tion is afforded, when we recall the fact that eniargination is confined to 

 a certain type of wing, and that when absent the wing is of an entirely 

 difTerent type as regards its general form. The wing of the frigate- 

 bird well illustrates the form of wing in which there is no such 

 eniargination. It is a very long, acutely pointed wing, in which the first 

 primarj' is the longest, the second, third, and all of the following being 

 successively shorter, and all sharply pointed, so that when the wing is 

 fully extended there is practically no open space between the tips of any 

 of the primaries. 



" There are three principal types of wing in relation to its form : 



"I. A very long, pointed wing, in which the first primary is the 

 longest, and all the outer primaries are narrowed toward the tip, and 

 successively decrease rapidly in length, rendering no emargination neces- 

 sary. Examples : man-of-war birds, albatrosses, shearwaters, gulls, terns, 

 plovers, sandpipers, swallows, swifts, etc. 



" II. A short, rounded wing, in which the tip is formed by the four 

 or five outer primaries, which are sub-equal in length. Here, owing to 

 the shortness of the wing, the tips of the primaries are not separated when 

 the wing is fully extended. Here no emargination is necessary, and none 

 exists. Examples : sparrows, and the smaller song-biids in general; also 

 rails, quails, tinamous and many grouse. 



" III. A long, pointed wing, but in which the tip is formed not by 

 either the first or second primaries, but by the third, fourth, and fifth, 

 and in which the six or seven outer primaries form the point of the wing, 

 and are graduated in length from the longest, which is about the fourth 

 or fifth, outwardly to the first, and inwardly to about the seventh or 

 eighth. This form of wing, in which emargination is present, is typically 

 exemplified in hawks, eagles, buzzards, vultures, ravens, crows, etc. 



" Between these types of wing there is every stage of intergradation, 

 with corresponding variation in the emargination of the primaries, in the 

 form of wing characterized by this structure. The true falcons have a 

 very pointed wing, in which the longest primary is the second ; the first is 

 somewhat shorter, and is the only quill showing emargination. In this 

 the emargination is slight, and extends for only about two inches. If we 

 remove the first primary, we have a wing in which the outer primary is 

 the longest, the next succeeding primaries being each shorter than the 

 one next in front, resulting in a long pointed wing, in which the primaries 

 are narrowed toward the tip, and recede successively in length, giving 

 the same form of wing we have in the man-of-war birds, in swallows. 



