122 THE AMERICAN NATURALIST [Vol. XL V 



From analogy to terrestrial forms, the photogenicity 

 and coloration of marine organisms must play some 

 essential" part in their life histories; 



The absence of definite organs for the reception of the 

 radiations of light may not necessarily indicate that the 

 forms from which they are absent are insensible to these 

 radiations; 



' The photogenic function in certain simple marine 

 forms may replace the olfactory function of terrestrial 

 forms, to some extent. 



