ADAPTIVE CHANGES IX COLOR OF FUNDULUS. 67 



lights to which the fishes were exposed, is definite proof that in 

 Fundiilitt. the quality or wave-length has a specific effect apart 

 from quantity of light or intensity. That the responses to the 

 variou> colors is here not so pronounced as in experiments where 

 fishes were placed in colored boxes and exposed to diffuse day- 

 light f L-ks, is due to the fact that the fishes were ex- 

 posed to spectral lights for only five day periods. Moreover, the 

 area and brightness of the colored environment were much re- 

 <lu< 



1\ . Tin, BASIS OF ADAPTIVE CHANGES IN SHADE AND COLOR. 

 A. The Normal Coloration. 



1 In reshly taken from the sea varied greatly from 



a yell- n to black when seen from above. The silvery 



liars of tin- adult male with scattered yellow and bronze colored 

 .spot- an very conspicuous on specimens otherwise dark. The 

 l-urs are due to the smaller number of melanophores superficial 

 to the -rales and to the presence of dense groups of guanophores 

 or irid which are frequently arranged like branched fila- 



ments. The guanophores are highly refractive and when viewed 

 by rei <\ li^ht, reveal the whole gamut of colors. 



A -ly stated all specimens were made to assume the 



pale vcllo :i tint by being placed for several days in a white 



dish I.. ,-ing subjected to the various other colored environ- 



ments. It". no\v. the living specimens be examined by reflected 

 liijit under a microscope or with a good hand-lens, it will be seen 

 that tl re than enough material to work on to account for 



the col.iratio: < aled in the various experiments. The most 



striking phenomenon is the presence of brilliant points scattered 



r the dorsal and lateral surfaces. This is especially prominent 

 when direct sunlight is allowed to fall on the fish. The bright 

 point- o.vupy the central portion of many melanophores and in 

 their dark setting appear like jewels. The phenomenon in due to 

 an association of iridescent giianophores or iridocytes with melan- 

 ophores. 



further detailed study of the color elements, fresh speci- 

 mens from each of the colored environments were fixed by dip- 

 ping them in hot w.ater for about 10 seconds, then in cold and 



