COLOR OF THE AMBLYOPSID^. 77 



nective tissue separates successive myotomes. On the sides of the tail the pigment 

 is dense on either side of these colorless lines. A dark band extends along the sides 

 of the head through the eye. The top of the head is dark (plate i, fig. a). 



The pattern of Chologaster cornutus agrees with that of C. papiUiferus. The 

 longitudinal bands are much darker and wider and without the light central 

 streak. The middle band is much wider than the others and is continued forward 

 to the tip of the snout. The amount of color present varies very greatly with the 

 locality from which the specimens come. 



The general color of C. agassizii is light gray (plate 6, upper figures). The 

 scales are lighter than the area surrounding them. The color pattern is more striking 

 than in the other species of the genus. Each somite is bordered by a dark line. The 

 lines of successive somites are separated by an almost imperceptible colorless line. 

 A broad, not sharply defined, band extends along the sides. The middle of this is 

 lighter than the margin. Another one extends between the somites and the ven- 

 tral musculature, another from the nape between the lateral somites and the dorsal 

 muscles, and a diverging one from near the nape to either side of the dorsal fin. 

 Dark areas are caused by the accumulation of pigment along the borders of the 

 small muscles of the fins. Still another dark area is found about the caudal. The 

 ventral surface is white, except the accumulation of pigment along the lines sepa- 

 rating the muscles. The fins are uniformly light gray. A light area is found on 

 both the upper and lower part of the caudal peduncle, just within the first short 

 rays of the caudal. 



The general color of Typhlichthys is cream and pink. It is abundantly pig- 

 mented. In younger specimens the pigment is arranged in more definite areas 

 about the head. In the old it is more uniformly distributed, being, however, spe- 

 cially abundant about the brain. The pigment pattern of the body is precisely as 

 in Chologaster except that the individual pigment cells are minute and their aggre- 

 gate not evident except under the lens. 



The retention of the color pattern of Chologaster in Typhlichthys is not less 

 interesting than the retention of similar habits. It is perhaps due to different 

 causes. The color pattern in Chologaster is determined by the underlying mus- 

 cular structure and the retention of a similar pattern in Typhlichthys is due to the 

 same underlying structure rather than to the direct hereditary repetition of the 

 color pattern. In Amblyopsis the color is much less marked than in Typhlichthys. 

 Amblyopsis is flesh-colored, ranging to purple in the gill-region, where the blood of 

 the gills can be seen through the overlying structures, and over the liver, which can 

 be seen through the translucent sides and ventral wall. About the head and bases 

 of the fins the color is yellowish, resembling diluted blood. The surface of the body 

 is slightly iridescent and that of the head has a velvety, peach-bloom appearance. 



The general pink color of Amblyopsis is due to the blood, not to any abnormal 

 development of blood-vessels in the dermis. In the fins where the blood-vessels 

 are near the surface, the general effect is a yellowish color. The surface vessels of 

 the dermis also appear yellowish. It is only on account of the translucent condi- 

 tion of all the tissues, permitting the deeper vessels to show through a certain thick- 

 ness, that the pink effect is produced. Amblyopsis has always been spoken of as 

 white. The term "white aquatic ghosts" of Cope is very apt, for they do appear 

 white in the caves and their gliding motion has an uncanny effect. All alcoholic 

 specimens are white: 



