Scales of Insects and Fish. 51 



too long a dissertation on the laws of light and colour ; 

 but so it is. And when this polarized ray is either 

 thrown upon or transmitted through various sub- 

 stances, it is either reflected, or absorbed and extin- 

 guished, according to the structure of the object 

 presented to it. The most brilliant colours are de- 

 veloped by this process, especially in crystals, feathers, 

 sections of quill, bone, hoof, horn. A good selection 

 of these objects is of value to the microscopist." 



