Fig. 1. — A Mediterranean flounder, Rlwinboidichthys podas, show- 

 ing color pattern displayed by the fish upon a bottom of coarse, dark 

 sand, containing white particles. 



Fig. 2. — The same specimen as tliat shown in Fig. 1, after transfer 

 to a bottom of fine gravel. (Compare carefully the markings in the 

 two cases.) 



