50 THE THEORY OF NATURAL SELECTION 



tive contrivances may run away with him if not kept 

 well in hand. For there is scarcely any limit to the num- 

 ber of problematical cases which have been described 

 as adaptive resemblances, and so explained as having 

 arisen through natural selection, whilst the evidence 

 in favour of such a supposition is in many cases highly 

 questionable. On the other hand, in a number of 

 well-marked instances, the theory of mimicry certainly 

 seems to afford an adequate explanation of the way 

 in which many curious characters and structures may 

 possibly have come into existence. 



The family of the mantises, including the walking- 

 stick and leaf insects, affords many examples of 

 animals which both in their colour and configuration 

 show a very close resemblance to surrounding inanimate 

 objects. This resemblance must have the effect of 

 concealing them from their enemies, and more particu- 

 larly from their prey, as, indeed, a study of their 

 habits indicates quite clearly. 



Phyllopteryx, an Australian fish allied to the well- 

 known sea-horse (Hippocampus), is provided with a 

 number of irregular appendages of ragged skin 

 resembling the seaweed amongst which this animal 

 is found. In this way the characteristic symmetrical 

 appearance of a live animal is got rid of, and the 

 creature is rendered extremely difficult of observation. 

 Here, againj the concealment afforded is probably 

 useful in leading to the deception of the smaller fishes 

 upon which the creature feeds. 



Examples of this kind in which the shape of an 

 animal leads to its concealment are comparatively 



