68 



of thin plates or ridges in the scales ; this is called " lamellar 

 coloring." There are certain bodies called iridocytes (rainbow 

 plates) imbedded in the epidermis which have an important 

 function, it is said, in this iridescent play of colors. 



The coloration is, however, chiefly dependent on the ar- 

 rangement of the pigment cells or cliromatopJiores, which lie 

 in the lower strata of the epidermis. These are black, yellow 

 and red ; the latter, according to Pouchet, being capable of 

 dimorphic changes into blue and green. The combinations 

 of the various hued cJiromatophores with the metallic crystals 

 of silver, the white of the bony scale plates showing through 

 the epidermis, and the iridocytes already referred to, produce 

 the coloration of every kind of fish. 



An embryonic fish is colorless, but the pigment cells of 

 black, yellow and red soon begin to appear, as is shown in 

 Alexander Agassiz's beautiful plates of the early stages of 

 flounders and other species, published in the BiiUetiii of 

 the Museum of Comparative Zoology. When the black pig- 

 ment predominates, the color is sombre, as in the adult tautog, 

 Tautoga onitis. A slight admixture of yellow gives the 

 bronze-like hue of the eel, and a little more of the same re- 

 sults in the brighter green of the black-bass, the blue-fish and 

 the cunner. In all of these there is a sprinkling also of red, 

 giving the warmer brownish greens so often seen in these 

 species. Red pigments intermixed with black give the dingy 

 browns of the carp, the sculpins and some of the cat-fishes. 

 When the yellow and red outnumber the black cells, there 

 result the tawny colors of the sand-dabs, the sun-fishes, the 

 cusks and the ling, and of some varieties of the cod. Red 

 chromatophores alone cause the brilliant scarlet of the red 

 snapper and the rose-fish, and when these are interspersed 

 with black, the deeper colors of the mangrove snapper and 

 the ruddy variety of the sea-raven. When the chromato- 

 phores begin to segregate into separate groups according 

 to color, the result is the formaticy of bands, stripes, 

 spots and shadings infinite in their possibilities of muta- 



