114 FAMILY CHARACTERISTICS. 



while the Seal has a continuous uniform outline 

 adapted for swimming. They form separate 

 Families, and are easily recognized as such l>y the 

 difference in their external outline ; hut what is 

 the anatomical difference producing the peculiar- 

 ity of form in each, hy which they have heen 

 thus distinguished ? It lies in the structure of 

 the limbs, and especially in that of the wrist 

 and fingers. In the Seal the limbs are short, and 

 the wrists are on one continuous line with them, 

 so that it has no power of bending the wrist or 

 the fingers, and the limbs, therefore, act like flap- 

 pers or oars. The Bear has a well-developed paw 

 with a flexible wrist, but it steps on the whole 

 sole of the foot, from the wrist to the tip of the 

 toe, giving it the heavy tread so characteristic of 

 all the Bears. The Dogs, on the contrary, walk 

 on tiptoe, and their step, though firm, is light, 

 while the greater slenderness and flexibility of 

 their legs add to their nimbleness and swiftness. 

 By a more extensive investigation of the anatom- 

 ical structure of the limbs in their connection 

 with the whole body, it could easily be shown 

 that the peculiarity of form in these animals is 

 essentially determined by, or at least stands in 

 the closest relation to, the peculiar structure of 

 the wrist and fingers. 



Take the Family of Owls, as distinguished 

 Hm the Falcons, Kites, etc. Here the differ 



