" EXPLANATION OF PLATES. 



All of the figures found in the following plates are reproductions of photographs and 

 autochromes from life, none of which have been retouched, tinted, or altered in any way. 



Plates XIX, XX. — Adaptation on natural backgrounds. 



Plate XIX. 



Fig. I. Paralichihys albiguttus, 20 cm. long, on fine variegated shells, yellow predominatilig, partly 

 buried as usually found in nature. 



Fig. 2. Same individual two minutes later with the shells removed. 



Fig. 3. P. albiguttus, 21 cm. long, on coarse shells of the same kind, partly buried, from August 16 

 to 19. 



Fig. 4. Same individual two minutes later with shells removed. Note that the pattern is much 

 coarser than xa figure 2 on the fine shells. In both the skin was distinctly yellowish in color. 



Plate XX. 



Fig. 5. Same individual as in figure 4 on very fine gray sand, almost entirely covered with sand. 

 From August 19 to 21. Note the two small depressions in the sand at the base of the caudal fin. The 

 lower one is much more prominent than the other. This individual breatlied only through the lower 

 gill. The water which entered the mouth passed back under the body and oozed up through the sand, 

 forming the depressions. The animal was very effectively concealed. 



Fig. 6. Same individual uncovered. Compare with figure 4 and note what a great change took 

 place in the pattern. The skin also changed very much in color. All the yellow had disappeared and 

 it had assumed a light gray shade. 



Fig. 7. P. albiguttus, 13 cm. long, in a glass dish over very fine black sand. Note the remarkable 

 similarity between the pattern and the shade in the fish, especially the central part of the body, and 

 those of the sand. The tips of the fins and the tail h^e no pigment and consequently stand out boldly 

 against the background. 



Fig. 8. P. albiguttxis, 16 and 10 cm. long, on a smooth jet black background. Note the conspicu- 

 ous white spots. In some instances all of these, except a trace of the one at the base of the pectoral fin, 

 disappeared entirely. 



Plates XXI— XXIII. — Adaptation on artificial black and white backgrounds. 



Plate XXI. 



Fig. 9. Paralichihys albiguttus, 14 cm. long, individual (B), on black and white background (2 mm. 

 squares) from July 29, 11 a. m., to July 30, 3 p. m., after having beenadapted to the background shown 

 in figiu'e 10. This individual was extensively used in the study of adaption on artificial backgrounds. 

 It is represented in many of the following figures. Note that numerous dark spots have appeared in 

 the light areas shown in figure 10, and that the light spots in the dark areas have become more ntunerous 

 and more conspicuous. 



Fig. 10. Individual (B) on black and white background (5 mm. squares) from July 25, 2 p. m., 

 to July 26, 11.30 a. m., after having been adapted to a white background. Note that the three very 

 light gray areas around the ocelli, shown in figiu'e 13, have become much darker and other dark spots 

 have appeared. 



Fig. II. Individual (B)on black and white background (2 cm. squares) from August i, 9 a. m., to 

 4.30 p. m., after having been adapted to i cm. squares, shown in figure 12. Note that the pattern has 

 changed very little. 



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