78 



11 VLB XEIGHB OKS 



it exists perfectly in the quaint little sea-horse 

 (Hippocampus), which is a poor swimmer, and rests 



by hooking its tail 

 around a bit of sea- 

 weed or coral, or 

 through a hole in a 

 broken shell, thus an- 

 choring itself securely. 

 A service of the 

 same nature is per- 

 formed by the tail of 

 many birds that are 

 accustomed to climb 

 about the trunks of 

 trees, and cling to 

 upright rocks, etc., in- 

 stead of walking on 

 the ground or perch- 

 ing upon the branches. 

 Familiar examples are 

 the woodpeckers, nut- 

 hatches, creeping- 

 wrens (Certhiadae), and swifts. Whenever these 

 birds rest a moment they press the tail hard against 

 the bark or other surface to which they cling with 

 muscular toes, and lean upon it. Such a leverage 

 is very important to enable the woodpeckers and nut- 

 hatches to deliver their sturdy and repeated blows ; 

 and without such a support the swift could hardly 

 hold itself, as it does for long periods, at rest 



^-•rr 



-\\ 



Prehensile Tail of the 

 Sea-horse. 



