ORIGIN OF THE SPECIFIC TYPE 321 



a leaf- adaptation, for there would still be wanting the instinct which 

 compels the butterfly, when it settles down, to hold the wings in such 

 a position that the two pictures on the anterior and posterior wiugs 

 fit into each other. Correlated mutations of the nervous system 

 suited to this end are required, but that is too much to attribute to 

 happy chance ! The same holds true in regard to the whole leaf- 

 picture on the two wings, for it could not possibly have arisen as a whole 

 by a sudden mutation. The whole litany of objections which have 

 been urged throughout several decades against the Darwin- Wallace 

 theory of natural selection, which were based on the improbability 

 that chance variations not in a definite direction should yield suitable 

 material for the necessary adaptations, may be urged much more 

 strongly against mutations, which make their appearance in much 

 smaller numbers and with less diversity. 



But it is — as we have already seen — in regard to the necessity 

 which exists almost everywhere for the- co-adaptation of numerous 

 variations of the most different parts, that the ' mutation theory ' breaks 

 down utterly. The kaleidoscopic picture, the mutation, is implicit 

 from the first, and must be accepted or rejected just as it is in the 

 struggle for existence ; but harmonious adaptation requires a gradual, 

 simultaneous, or successive purposive variation of all the parts con- 

 cerned, and this can be secured only through the fluctuating variations 

 which are always occurring, and are increased by germinal selection 

 and guided by personal selection. 



Many naturalists, and especially many botanists, regard adapta- 

 tion as something secondary, something given to species by the way, 

 to improve the conditions of their existence, but not aflfecting their 

 nature — comparable perhaps to the clothing worn by man to protect 

 himself from cold ; but that is hardly the real state of the matter. 



The deep-sea expedition conducted by Chun in 1898 and 1899 

 made many interesting discoveries in regard to animals living in the 

 depths of the ocean, all of which exhibit peculiar adaptations to 

 the special conditions of their life, and especially to the darkness of 

 the great depths. One of the most striking of these discoveries was 

 that of the luminous organs which are found not in all but in a great 

 many animals living on the bottom of the abyssal area, and also among 

 the animals occurring at various levels above the floor of the abyss. 

 These are sometimes glands which secrete a luminous substance, but 

 sometimes complex organs, ' lanterns ' which are controlled by the will of 

 the animal, and suddenly evolve a beam of light and project it in 

 a particular direction, like an electric searchlight. These organs have 

 a most complex structure, composed of nerves and lenses, which focus 

 II. Y 



