BEHAVIOR OF VERTEBRATES 431 



The markings of the underlying surface were most effective 

 in calling forth the changes. The markings on the vertical 

 walls of the tank although effective were less important, while the 

 overhead environment exerted little or no influence. 



The fish seems to make no direct comparison between its 

 body and the background. Adaptive changes occur when the 

 fish is buried in the sand and when its body (eyes excepted) is 

 coveied with a cloth. 



The changes in some way are conditioned upon optical pro- 

 cesses, since at least one eye must fuction normally if the changes 

 are to occur. If blinded when in the dark condition, the fish 

 ordinarily remained dark; if blinded in the pale condition, they 

 remained in that state for about a day and then reverted to 

 a darker condition. 



The author is conservative in his statements throughout and 

 rests content largely with stating his findings. The photographs 

 are excellent and on the whole convincing. The reviewer feels 

 that the patterns shown in the photographs could have been 

 somewhat better evaluated if Sumner had photographed along 

 with the flatfish some fish rather constant in its color tone and 

 pattern, and one which does not undergo such adaptive changes. 

 In many cases, though, the author has photographed the flat- 

 fish in pairs in such a way as to leave no room for questioning 

 the pronounced effect upon the pattern of the fish of changes 

 in the backgrounds. 



Werner (28) calls attention to the sleeping attitudes of sev- 

 eral species of fishes {Amiurus nebulosus, Misgurnns jossilis and 

 Cubitus talma). Sleep is needed by all members of the groups 

 particularly studied (Silurus glanis and Cobitus barbatula) but 

 the bodily attitudes taken are quite different even in the nearly 

 related races. In general there is a complete cessation of activ- 

 ity, a certain chosen bodily attitude, and almost complete stop- 

 page of breathing. Very light contact is sufficient to reawaken 

 the fish. 



Romeis (21) takes up in detail the peculiar movements of 

 the Maulbruter (Paratilapia multicolor) in seeking during the 

 breeding season a resting place under the leaves of certain 

 water plants. When in the neighborhood of the thickly matted 

 plant leaves, it interrupts for some seconds the lively play of 

 its fins, swims slowly here and there, and when a suitable place 



