Body Covering 43 



nent pattern, brought about in some way by hormones gen- 

 erated by the ripening sex-products. 



But there is one group of fish well-known to the aquarist 

 whose nuptial brilliance does depend on chromatophores. 

 These are the cichlids — the scalares, the orange chromides, 

 the acaras, and, most striking of all, the already-mentioned 

 "jewel." This little fish from tropical Africa spawns with 

 great frequency, sometimes oftener than once a week, and 

 it might be supposed that the flaming color which it puts on 

 for each occasion, and which fades to a dull gray in the 

 interludes, is again an effect of generative hormones. There 

 is this difference, however, between it and such a fish as the 

 trout, that the latter retains its nuptial colors in unvarying 

 brilliance until the sex-products are disposed of, whereas the 

 jewel, male or female, will lose its color and revert to the 

 pale gray of the unripe fish if it is caught by a human hand 

 or cowed by a more powerful rival, to reacquire its brilliance 

 as soon as it is undisturbed. The courting dress is therefore 

 due not to a direct secretion of the ripe ovaries or testes act- 

 ing upon the coloring agents, but to an excitement brought 

 about by the ripeness of the sex organs, which excitement 

 stimulates the nerves which control the chromatophores. 

 That this is the case is further illustrated by the fact that 

 the administration of a drug called yohimbine to the male or 

 female jewel in its neuter, or unripe, stage will produce the 

 courting costume, without any of the courting behavior, and 

 this is because yohimbine acts upon the controlling nerves 

 and disperses the pigment throughout the chromatophores. 

 The artificial blushes will remain for three or four days, 

 gradually disappearing as the effects of the drug wear off. 



"How" and "why" are the two questions which man is 

 always asking. Long before the "how" of nuptial coloring 

 had been considered, the "why" was being asked, and 

 Charles Darwin himself gave one of the first answers in his 



