LIGHT -PRODUCING ORGANISMS 19 



a light for any practical purposes. The history of Science 

 teaches that it is well never to say that anything is impos- 

 sible. It is very unlikely that any luminous animal can 

 be utilized for practical illumination, but there is no 

 reason why we cannot learn the method of the firefly. 

 Then we may, perhaps, go one step further and develop 

 a really efficient light along similar lines. To what extent 

 our inquiry into the "secret of the firefly" has been suc- 

 cessful may be gleaned from the following pages. 



