OUR FACE FROM FISH TO MAN 



of the facts cited in the present chapter.' The 

 lower forms of animals exhibit a wide diversity of 

 organs sensitive to light, in various stages of 

 complexity. Too long exposure to the ultra- 

 violet rays has an injurious or even fatal effect on 

 many organisms, such as bacteria, infusoria, 

 hydroids, rotifers, nematodes, etc. (Plate, 1924, 

 p. 386), which hence shrivel up or shrink away 

 from these rays, while as everyone knows, plants 

 turn toward the sunlight and some animals love to 

 bask in the sun. Hence in view of the importance 

 of light to the organism in one way or another, it 

 is not surprising that even in very simple one- 

 celled forms such as certain protista there should 

 be clear granules, like lenses, sometimes backed by 

 dense pigment, which may in some way act as 

 rudimentary eyes and contribute to the organism's 

 different reactions to light of different intensities 

 (Plate, 1924, pp. 424-427). At any rate, when 

 we come to certain of the jellyfishes we find 

 undoubted eyes or ocelli in the outer layer or 



' Professor Plate {in litteris) calls attention to the fact that, con- 

 sidering the enormous range of electric waves (from almost zero to 

 hundreds of kilometers), it is remarkable that the whole gamut of 

 human sensation of light, color, form and movement, with all their 

 derived pleasures, is caused by so relatively narrow a range of electric 

 waves. " How different our picture of the world would be," he 

 writes, " if we had more such regions! " 



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