The Problem of Adaptation 9 



theless, if the color is useful to its possessor, it is an adapta- 

 tion in our sense of the word, without regard to the way in 

 which it has been acquired. Even, for instance, if the resem- 

 blance were purely the outcome of chance in the sense that 

 the color appeared without relation to the surroundings, it 

 would still be an adaptation if it were of use to the animal 

 under the ordinary conditions of life. 



In the lower groups numerous cases in which animals 

 resemble their surroundings could be given. Such cases are 

 known in Crustacea, worms, mollusks, hydroids, etc., and the 

 possible value of these resemblances may be admitted in 

 many instances. 



It is rather curious that so few cases of adaptive color- 

 ation have been described for plants. No one supposes 

 that the slate color of the lichen is connected with the color 

 of the rocks on which it grows, in the sense that the resem- 

 blance is of any use to the lichen. Nor does the color of the 

 marine red algae serve in any way to protect the plants so 

 far as is known. The green color of nearly all the higher 

 plants is obviously connected with the substance, chlorophyl, 

 that is essential for the processes of assimilation, and has 

 no relation to external objects. But when we come to the 

 colors of flowers we meet with curious cases of adaptation, 

 at least according to the generally accepted point of view. 

 For it is believed by many naturalists that the color of the 

 corolla of flowering plants is connected with the visits of 

 insects to the flowers, and these visits are in many cases 

 essential for the cross-fertilization of the flowers. This adap- 

 tation is one useful to the species, rather than the individual, 

 and belongs to another category. 



The leaf of the Venus's fly-trap, which suddenly closes 

 together from the sides when a fly or other light body 

 comes to rest on it, is certainly a remarkable adaptation. 

 A copious secretion of a digestive fluid is poured out on the 

 surface of the leaf, and the products of digestion are absorbed. 



