450 THE ZOOLOGIST. 



suggestion : Certain tan-spots occur over the eyes of semi- 

 domesticated Dogs. They do not exist in wild animals allied to 

 the Dog, or in the modern breeds of fully-domesticated Dogs. 

 The spots are most conspicuous when the eyes are closed, 

 appearing then like opened eyes. They " may have been pro- 

 tective to the animals during sleep, causing them to look as if 

 wide awake." This speculation has been supported by no less 

 an authority than Mr. A. R. Wallace.* Waterton, in describing 

 the South American Sloth, writes : "His fur has so much the hue 

 of the moss which grows on the branches of the trees that it is 

 very difficult to make him out when he is at rest."t The 

 Philippine Koel, or Phow (Eudynamis mindanensis), one of the 

 Cuckoos, is an example of a bird in which the young does not 

 follow the general rule of having the plumage of the female, or 

 one distinct from that of both parents. Mr. Whitehead accounts 

 for this by the fact of the Phow laying its eggs in the nest of the 

 Yellow-wattled Myna. " The young Cuckoo, being black, does 

 not differ from the young Myna, and so the deception is carried 

 on until the young bird can take care of itself. If the young 

 followed the general rule, and resembled their mother in being of 

 a brown colour, the Mynas might not feed them." + Of the 

 Matamata Tortoise (Chelys ftmbriata), a South American species, 

 it has been observed : — " When in its native element the warty 

 appendages on the neck float in the water like some vegetable 

 growth, while the rugged and bossed shell strongly resembles a 

 stone ; it is thus probable that the whole appearance of the 

 creature is advantageous either in deluding its enemies or in 

 attracting to it the animals on which it feeds, the latter being the 

 most likely hypothesis. Although it appears that the Matamata 

 will occasionally eat vegetable substances, its chief food consists 



* ' Nature,' vol. li. p. 533. 



f ' Wanderings,' Wood's edit. p. 219. — We may here refer to " the law 

 which underlies Protective Coloration " as propounded by Mr. Abbott H. 

 Thayer, the law of gradation in the colouring of animals, which "is respon- 

 sible for most of the phenomena of protective coloration except those properly 

 called mimicry. . . . Mimicry makes an animal appear to be some other 

 thing, whereas this newly-discovered law makes him cease to appear at alJ." 

 Thus " animals are painted by nature darkest on those parts which tend to 

 be most lighted by the sky's light, and vice versa.'' 1 (Cf. ' The Auk,' vol. xiii. 

 1896 ; and reprint ' Ann. Eept. Smith. Instit.' for 1897, p. 477). 



I Cf. ' Royal Nat. Hist.' vol. iv. p. 7. 



