EFFECTS OF TEMPERATURE. 15 



or eight days in the chrysalis state ; this would be in 

 the heat of summer. Then, in the spring, the change 

 occupies a fortnight; but when the caterpillar enters 

 the chrysalis state in the autumn, the butterfly does 

 not make its appearance till the following spring. 

 Furthermore, it has been proved by experiment, that if 

 the condition of perpetual winter be kept up by keep- 

 ing the chrysalis in an icehouse, its development may 

 be retarded for two or three years beyond its proper 

 time; while, on the other hand, if in the middle of 

 winter the chrysalis be removed to a hothouse, the en- 

 closed butterfly, mistaking the vivifying warmth for 

 returning summer, makes its debut in ten days or a 

 fortnight. 



