DWELLINGS 1601 



tective to it. If, however, the animal is confined to 

 a Dahlia versicolor, it conforms to the hue of its new 

 abode that is, the pink one turns to red, and, in like 

 manner, if transferred to the yellow snapdragon, it 

 takes the color of this flower. They change in shade 

 as the shade of their host changes, and when pink, 

 white, green, and yellow varieties are confined to- 

 gether in a box they all become nearly white. 



The question of protective coloration in fishes has 

 of late received some light which compels a revision 

 of our former theories on the subject. It has usually 

 been held that the color of fishes is of the mimicry 

 order that is, it has been acquired for the purpose 

 of deceiving their enemies. Trout will very com- 

 monly take the hue of the river bottom over which 

 they swim, and, as every one knows, it is difficult to 

 detect a flounder or other flat fish at rest, though 

 when it turns over the white under surface of its 

 body instantly reveals the creature's presence. The 

 hue of the upper surface is due to the action of light. 

 For when a sole was kept in a raised glass case, with 

 light directed upward from below, pigment formed 

 on the white side, and began to be absorbed on the 

 one hitherto exposed to the same agent. 



DWELLINGS. FRDRIC HOUSSAY 



ANIMALS construct dwellings either to protect 

 themselves from the cold, heat, rain, and other 

 chances of the weather, or to retire to at moments 

 when the search for food does not compel them to be 

 outside and exposed to the attacks of enemies. Some 



