1904.] PACKARD— ORIGIN OF MARKINGS OF ORGANISMS. 441 



primarily due to the abundance of light and heat, there being no 

 great or sudden changes of temperature or of the chemical compo- 

 sition of the water ; while there is an abundant food supply brought 

 by the tidal currents from the surface of the ocean. Prof. Hickson 

 thinks that the brilliant tints, spots and stripes seen on polyps, 

 prawns, octopods and fishes are due to the fact that they live among 

 the brilliant surroundings of the coral reef: ''or, to put it in 

 another way, animals similarly organized and of similar habits 

 would be at a disadvantage on the coral reefs if they were not so 

 marked and colored." The other fishes of the tropics, he observes, 

 do not possess these curious and beautiful characters ; the sharks, 

 bonitos, flying fishes, herrings and others that do not live habitu- 

 ally on the coral reefs are not unlike in general color and ornamen- 

 tation the fish of temperate seas. Hence, these characters of coral- 

 reef animals are not directly due to the high tonperature and bright 

 light of the tropics, but are due to the character of the surroundings. 

 He adds that most of the tints are concealment colors. The only 

 example of what appears to be a warning color that he noticed 

 occurs in connection with the spines on the tails of certain surgeons 

 and trigger fish. Acanthurus achilleSy for example, has a uniform 

 purple color, but there is a bright red patch surrounding the 

 formidable tail spines that give these fish the name of surgeons. 

 Similar warning colors are very pronounced also in Naseus unicor- 

 nis and N. lituratus, and in some of the Balistidae. 



1 8. The Lack of Color-Patterns in Deep-Sea Fishes and 



Crustacea as contrasted with those of Shoal 



Sunlit Waters. 



Alcock, in his Naturalist in Indian Seas, states that the major- 

 ity of deep-sea fishes are of uniform usually sombre color, only a 

 minority in that ocean being banded, striped, or otherwise marked 

 in definite patterns. To enter into details: of 1 68 species dredged 

 below the loo-fathom line, fifty-two were black or some shade of 

 blue or purple-black; fifty-six were dull brown; ten were silvered 

 over a blackish or brownish ground color ; ten were bright silver ; 

 four gray — thus 78 per cent, were simply-colored species. Fourteen 

 species living between 100 and 250 fathoms were nearly uniform red 

 or of a rosy hue. Only eighteen species, and those dredged near 

 the IOC-fathom line, were striped or marked with patterns, and only 

 four were brilliantly variegated with many colors. 



