SEVENTH LECTURE. 



ON THE PHYSICAL BASIS OF ANIMAL PHOS- 



PHORESCENCE.i 



S. WATASfi. 



Whatever view we may take as to the nature of vitality, it 

 is evident that we can know Hfe only through the physical, 

 chemical, or mechanical manifestations, which an organism 

 displays at various phases of its existence. Our organs of 

 sense, which supply directly or indirectly the material of 

 human knowledge of both the animate and inanimate world, 

 are only related to force, or are set into a state of excitation 

 by motion of certain kinds, which we call a stimulus. What- 

 ever view, therefore, a biological philosophy may lead us to 

 accept in regard to the ultimate nature of life, our primary 

 step in the study of vitality must begin with the examination 

 of its material manifestations. 



Among many physical phenomena manifested by the living 

 organism there are few so striking, and none appear so isolated, 

 as the phenomena of the emission of light. Thus, Darwin, 

 in his discussion of some special difficulties of the theory of 

 natural selection, says : " The luminous organs which occur in 

 a few insects, belonging to widely different families, and which 

 are situated in different parts of the body, offer, under our 

 present state of ignorance, a difficulty almost exactly parallel 

 with that of the electric organs," and "it is impossible to 

 conceive by what steps these wondrous organs have been 

 produced." ^ 



1 The present paper is part of three lectures on Animal Phosphorescence, 

 delivered at the Marine Biological Laboratory at Woods Holl, during the sum- 

 mers of 1894 and 1S95, ^^^ elsewhere. A monographic account of the subject, 

 with a full bibliography, will be presented in the near future. 



2 Darwin : Origin of Species. 



