96 STRUCTURE AND COMPARISON. 



one foot, sticking the other up behind. To keep a straight 

 course a swan swimming with one foot must " bear off " with 

 every stroke, just as a canoeman does when using a single- 

 bladed paddle ; otherwise he would swim in a circle. 



Some of the totipalmate birds are said to swim with both 

 feet together. We can see that such a stroke would be a very 

 strong, effective one. The feet would be held together like 

 an inverted triangle ; and the longest, strongest toes, the outer 

 ones, would form the lower edge of a V where the greatest 

 resistance would be met. With feet so placed a powerful 

 backward and downward stroke would bring every part of the 

 webbing into full use, and give a great impulse to the bird. 



FIG. 25. ZYGODACTYL (OR YOKE-TOED) FOOT OF WOODPECKER 

 (LIFE SIZE). 



After we get into the higher orders the feet differ less 

 noticeably; yet many oddities occur. Notice the yoke-toed 

 foot of the woodpeckers, the cuckoos, and the parrots, or the 

 still odder foot of the kingfisher, in which two of the toes are 

 grown together for a part of their length. 



What is the origin or use of such a foot never seems to have 



