118 NATURE AND LIFE. 



others shielded from the light. The tadpoles that were 

 shone upon, soon underwent the change into the adult 

 form, while the others either continued in the tadpole con- 

 dition or passed into the state of perfect frogs with great 

 difficulty. Thirty years later, Moleschott performed some 

 hundreds of experiments in examining how light modifies 

 the quantity of carbonic acid thrown off in respiration. 

 Operating on frogs, he found that the volume of gas ex- 

 haled by daylight exceeds by one-fourth the volume thrown 

 off in darkness. He established, in a general way, that the 

 production of carbonic acid increases in proportion to the 

 intensity of light. Thus, with an intensity represented by 

 3.27, he obtained 1 of carbonic acid, and, with an intensity 

 of 7.38, he obtained 1.18. The same physiologist thinks 

 that in batrachians the intensity of light is communicated 

 partly by the skin, partly by the eyes. 



Jules B6clard made more thorough researches. Com- 

 mon flies'-eggs, taken from the same group, and placed at 

 the same time under differently-colored glasses, all pro- 

 duce worms. But if the worms, hatched under the differ- 

 ent glasses, are compared at the end of four or five days, 

 perceptible differences may be seen among them. Those 

 most developed correspond with the violet and blue ray ; 

 those hatched under the green ray are far less advanced ; 

 while the red, yellow, and white rays exert an intermediate 

 action. A long series of experiments on birds satisfied 

 Be'clard that the quantity of carbonic acid thrown out in 

 breathing, during a given time, is not sensibly modified by 

 the different colors of the glasses the animals are placed 

 under. It is the same with small mammifers, such as mice ; 

 but it is to be observed in this case that the skin is covered 

 either with hair or feathers, and the light does not strike 

 the surface. The same physiologist examined also the in- 

 fluence of the differently-colored rays of the spectrum on 

 frogs. Under the green ray, the same weight of frogs pro- 



