334 /N LOWER FLORIDA WILDS 



this region are highly phosphorescent, and doubt- 

 less in places they are sufficiently abundant on the 

 bottom to furnish enough light for others to see. 



It may be wondered why in this darkness or 

 semi-darkness there is any rich coloring among 

 the animals, and the reason is not clear. There is 

 much to be learned about the economy of color in 

 organic life. Some of the more adventurous of 

 the littoral forms may have migrated slowly into 

 deeper water and, in other cases, animals of the 

 shallows unable to compete with stronger forms, 

 may have been driven to where conditions are 

 more favorable. Where this migration has been 

 recent, color and other shoal water characters 

 (though no longer needed) would still persist. 

 Many of these deep sea animals possess a peculiar 

 red which Alfred Mayer says shows black in the 

 depths, hence it may be protective. At all events 

 the majority of mollusks we took on the Pourtales 

 Plateau are neutral in color scheme, or develop 

 a pearly sheen probably protective in a dim light 

 or feeble phosphorescent glow. The most striking 

 exception among our catch is that of the Volutas 

 but Voluta is a shallow water genus, and our three 

 species are likely recent residents of the darker zone. 



