108 UTILIZATION OP MINUTE LIFE. 



that differently coloured light, or, in other terms, 

 the different rays of the solar spectrum, have a very 

 different influence upon the development of young 

 animals, on the hatching of eggs of insects, the 

 growth of larvae, etc. 



Many philosophers, from the time of Priestley 

 and Ingenhouz to the present day, have studied the 

 influence of light on vegetables, but few have paid 

 attention to its action upon the animal organism. 

 Thus, whilst Priestley, Ingenhouz, Sennebier, De 

 Candolle, Carradori, Knight, Payer, Macaire, and 

 some others, made manifest the action of light 

 upon vegetable respiration, absorption, exhalation, 

 etc. ; in a word, upon the phenomena of nutri- 

 tion and development in plants ; Edwards and 

 Morren were almost the only observers who studied 

 animal life from the same point of view. Edwards 

 showed that without light the eggs of frogs cannot 

 be developed, and that the metamorphosis of tad- 

 poles into frogs cannot be effected in absolute 

 darkness.* Again, Moleschott has recently shown 

 that the respiration of frogs is most active in the 

 daylight, diminishing considerably during the night; 

 and Charles Morren observed Infusoria to evolve 

 oxygen whilst basking in the sunbeams which 

 play upon the stagnant waters they inhabit. 



* Compare Higginbottam in "Proceedings of the Royal So- 

 ciety," 1862 ; where some experiments of Edwards are refuted. 



