354 Biology in America 



sustain roughly three times the pressure on the foundations 

 of the Woolworth Building or the Metropolitan Life. To 

 withstand such a pressure the body of an animal would have 

 to be surrounded by an exceedingly strong shell, or else it 

 must be of such a character that the pressure is easily ren- 

 dered the same within and without. The latter method is 

 the one which Nature has adopted, and the bodies of deep 

 sea animals are so soft and permeable that they lose their 



DEEP SEA FISHES AS SEEN AGAINST A LIGHT BACKGROUND. 

 Photograph of a group in the American Museum of Natural History 

 in New York. 



Courtesy of the Museum. 



shape very easily when brought to the surface and are 

 consequently hard to preserve in their natural form. 



Below depths of three thousand feet light is virtually absent 

 in the sea. Animals therefore living below this comparatively 

 shallow depth are in perpetual darkness, save for such light 

 as they themselves generate. Many of these deep sea forms 

 carry their own lanterns about with them in the form of 

 phosphorescent organs. The firefly is an object of common 

 experience to many a country dweller, but only the ocean 

 voyager or the inhabitant of its shores, who has seen the 



