Habits a/nd Adaptations 251 



tened that they are able to live on or very close to the bot- 

 tom. In the ray this brings the mouth down to where it can 

 easily scoop up the shell-fish which form its food. It is, 

 therefore, mainly a feeding adaptation. In the flounder, 

 however, it is more in the nature of a camouflage, for it 

 permits him to lie flat on the bottom where, with the help 



Figure 28. MALE BETTA UNDER HIS BUBBLE-NEST, 

 RELEASING ANOTHER BUBBLE 



of his changeable coloring, he escapes the notice not only of 

 his own prospective food but also of those forms which look 

 upon him as food. It is, therefore, both a feeding and a 

 protective adaptation. 



These explanations of purpose are, it must be admitted, 

 conjectural. But in determining the method by which the 

 adaptation is arrived at there is no need for conjecture. The 

 anatomical evidence is all there. The ray is a highly depressed 

 shark. It is compressed from top to bottom, just as if you 

 had taken a clay model of a shark and squeezed it between 

 two horizontal plates until it is almost flat. The ray, like 



