EGGS OF GLASS. 261 



found by the thermometer to be two or three 

 degrees above blood heat. The whole six pupae 

 were born in less than six days, while others of the 

 same species in a box in a window-seat were not 

 developed until twelve days later. As the heat 

 thus obtained seemed too violent for pupae to be 

 artificially reared with success, Reaumur suggests 

 that many variations might be made in the expe- 

 riments, which would have the effect of moderating 

 its amount. These experiments decided in the 

 most satisfactory manner the quickening influence 

 of increased warmth upon the pupae of insects. 

 Keaumur now became anxious to try the effects 

 of the opposite state of temperature, and to 

 ascertain whether exposure to cold would exer 

 cise any effect upon the pupae. It was reason- 

 able to imagine that as warmth had hastened 

 forward their development, cold would retard it. 



Eeaumur determined to try what would be the 

 result of putting his pupae in their boxes in a 

 cellar, and taking proper care to preserve them 

 from the damps of such a situation. He put them 

 there about the end of January. In ordinary 

 circumstances these pupae would have become 

 butterflies in the month of July in the same year. 



