THE CUCKOO AND HIS KINDRED. 115 



seems probable, although similar conditions of life 

 may account in some measure for a similarity in 

 external appearance between some of the Ground 

 Cuckoos and certain Game Birds. The number of 

 species and sub-species in the family CUCULID^E is 

 doubtless little short of two hundred ; and these are 

 distributed pretty generally over the great land- 

 regions of the globe with the exception of the Polar 

 areas. The great diversity of their appearance is 

 most remarkable, some species closely resembling 

 certain Game Birds in colouration ; others are 

 decked in the most brilliant hues, often of a lovely 

 bronze or metallic character. The range in size is 

 little less remarkable. The one constant external 

 character is the zygodactyle foot (two toes in front, 

 two behind, like that of a Woodpecker) ; it is not 

 known, however, whether any of the Cuckoos are 

 climbers, certainly so far as the typical Cuckoos are 

 concerned the feet are never used for such a pur- 

 pose. It seems probable that the peculiar form of 

 the Cuckoo's foot is either an inheritance from a 

 common ancestor, or, like so many other peculiari- 

 ties of structure, continues to be retained after its 

 service for some special function has ceased. The 

 serrated claw of the Goatsucker and the Heron may 

 be similarly explained. The general shape of the 



