440 COLYMBIDjE. 



streaked longitudinally with black and white lines ; breast, 

 belly and all the under surface of the body, pure white ; 

 flanks and under tail-coverts dusky ; legs and toes dark 

 brown outside, lighter pale brown within. The whole 

 length about twenty-six inches ; wing from the carpal 

 joint to the end of the primaries, eleven inches and a half. 

 Females are but little smaller than males, and both sexes, 

 when mature, have the throat black, as repeated internal 

 examinations have proved. The Divers undergo a partial 

 moult in the spring, and on the first assumption of the 

 Black-throat it is generally varied with a few white 

 feathers. 



Young birds measure twenty-three or twenty-four inches 

 in length, and closely resemble the young of the Northern 

 Diver, except in size. 



The form and structure of the legs and feet in these 

 Divers, and also in the Grebes, are worthy of particular 

 examination. Though almost useless on land, these mem- 

 bers are most efficient instruments in the water. The 

 bones are broad and flat, and almost as thin as the 

 blade of a knife ; when the backward stroke in swimming 

 is given, the whole surface of all these bones and their 

 investing membranes is brought to bear against the water ; 

 but when the leg is to be brought forward again to renew 

 the impulse, the sharp edges only are opposed to the 

 fluid, and the position, as well as the partially rotatory 

 motion, remind the observer of the action of oars in 

 rowing when used by skilful hands. Those who have 

 the opportunity of examining the legs of a Diver, in a 

 recently-killed specimen, while all the parts retain their 

 perfect flexibility, will find a beautiful example of animal 

 mechanics. 



