216 THE ARCTURUS ADVENTURE 



median light scales, either above or below the base 

 of the tail. 



From the very first I directed all my attention 

 to the possible utility of these lights. The lower 

 battery, when going full, cast a solid sheet of light 

 downward, so strong that the individual organs 

 could not be detected. Five separate times when 

 I got fish quiet and wonted to a large aquarium, I 

 saw good-sized copepods and other creatures come 

 within range of the ventral light, then turn and 

 swim close to the fish, whereupon the fish twisted 

 around and seized several of the small beings. 

 Once it turned completely on its back. I could 

 never have seen this except that the glass sides of 

 the aquarium reflected sufficient light. Whether 

 this is the chief object of the ventral lighting I do 

 not know, but it is at least occasionally effective. 



Perhaps the best distinction between various 

 species of this group of lantern fish is the arrange- 

 ment of the lateral light spots, — indeed in the 

 dark-room I could tell at a glance how many 

 species were represented in my catch by their lumi- 

 nous hieroglyphics. When several fish were swim- 

 ming about, these side port-holes were almost 

 always alight, and thus it seems reasonable to sup- 

 pose that they are recognition signs, enabling 

 members of a school to keep together, and to show 

 stray individuals the way to safety. 



The light scales of the tail are apparently of 

 great importance. Ordinarily when the whole fish 

 is glowing with the pale, cold, greenish light of 

 luminescence, these caudal lights are seldom seen. 



