264 DARWINISM chap. 



have a patch, of bare black skin round the eyes, and a ruff 

 of curious pale recurved feathers on the nape, whence their 

 name of Friar-birds, the ruff being supposed to resemble the 

 cowl of a friar. These peculiarities are imitated in the orioles 

 by patches of feathers of corresponding colours ; while the dif- 

 ferent tints of the two species in each island are exactly the 

 same. Thus in Bouru both are earthy brown ; in Ceram they are 

 both washed with yellow ochre ; in Timor the under surface 

 is pale and the throat nearly white, and Mr. H. 0. Forbes has 

 recently discovered another pair in the island of Timor Laut. 

 The close resemblance of these several pairs of birds, of widely 

 different families, is quite comparable with that of many of the 

 insects already described. It is so close that the preserved 

 specimens have even deceived naturalists ; for, in the great 

 French work. Voyage cle V Astrolabe, the oriole of Bouru is 

 actually described and figured as a honey-sucker; and Mr. 

 Forbes tells us that, when his birds were submitted to Dr. 

 Sclater for description, the oriole and the honey-sucker were, 

 previous to close examination, considered to be the same 

 species. 



Objections to the Theory of Mimicry. 



To set forth adequately the varied and surprising facts of 

 mimicry would need a large and copiously illustrated volume; 

 and no more interesting subject could be taken up by a 

 naturalist who has access to our great collections and can de- 

 vote the necessary time to search out the many examples of 

 mimicry that lie hidden in our museums. The brief sketch of 

 the subject that has been here given will, however, serve to 

 indicate its nature, and to show the weakness of the objections 

 that were at first made to it. It was urged that the action 

 of "like conditions," Avith "accidental resemblances" and 

 " reversion to ancestral types," Avould account for the facts. If, 

 however, we consider the actual phenomena as here set forth, 

 and the very constant conditions under which they occur, we 

 shall see how utterly inadequate are these causes, either 

 singly or combined. These constant c o nditions are — 



1. That the imitative species occur in the same area and 

 occupy the very same station as the imitated. 



2. That the imitators are always the more defenceless. 



