426 STUDIES IN GENERAL PHYSIOLOGY 



It is not to be wondered at that the various investigators 

 arrived at diametrically opposite results. 



Edwards states that frogs' eggs do not develop and soon 

 die when inclosed in a dark box, while the development 

 takes place in an open box which is exposed to the light, 

 According to Edwards, even the young larvae require a longer 

 time to develop in the dark than in the light. Edwards's 

 statements are based on very few experiments. Dutrochet 

 repeated the experiments of Edwards, and found that 

 where the supply of oxygen was sufficient and the tempera- 

 ture was the same in the two boxes, the eggs of Batrachians 

 developed as well and as rapidly in the dark as in the 

 light. These facts indicate that in Edwards's experiments 

 the eggs suffered from lack of oxygen and exposure to a low 

 temperature. 



Be"clard published a short communication on the influence 

 of light on the development of the eggs and the larvae of 

 flies. He placed the eggs under colored bell-jars, and found 

 that after four or five days development was most advanced 

 under the violet and blue jars, and least under the green. I 

 cannot understand the experiments of Be"clard, as fly larvae 

 hatch in about two days in summer, and up to this time their 

 size depends on the size of the eggs, since further growth 

 takes place only when the larvae find food in which to bury 

 themselves. The statements of Be"clard regarding the influ- 

 ence of light on the production of carbon dioxide in animals 

 are also doubtful. 



It is rather strange, though characteristic, that in the 

 scientific literature of our subject one frequently finds serious 

 mention of the investigations of General Pleasanton, made 

 on six pigs. The general put three pigs into a stall with 

 violet windows, and three into a stall with ordinary windows. 

 While the three pigs exposed to violet light gained 398 

 pounds in four months, the others gained during the same 



