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. ei he obtained 1 of carbonic acid, and, with an intensity 
7.38, he obtained 1.18. The same physiologist thinks 
ae in batrachians the intensity of light is communicated 
partly by the skin, partly by the eyes. 
Jules Béclard 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 
Béclard 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- 

