482 



to the action of natural causes, terminates in the spontaneous produc- 

 tion of the young insect, reciprocally with the first growth of its appro- 

 priate leaf, when spring has far advanced. But to render exotic mul- 

 berrys, which have been retarded by annual transplantation, available, 

 it has been necessary to retard in a corresponding degree the hatching 

 of the egg. This can only be accomplished by subjecting it to the 

 continued action of low temperature, somewhere between the freezing 

 point and the 45° of the thermometer. This state should commence 

 before the egg has felt the slightest influence of the vernal heat, and 

 the method I adopt is to deposit early in March a tin box, containing 

 the eggs, in contact with ice, and so keep them until wanted. In this 

 way they have been known to keep two years and hatch well. 



The eggs employed in my experiment were removed from the ice- 

 house on the 20th day of July, and as an intermediate state between a 

 low and high degree of temperature, they were placed in a cool cellar 

 for a few days, and then subjected to the 



TEMPERATURE OF THE HATCHING-ROOM. 



Nearly the entire amount hatched vigorously on the tenth and elev- 

 enth days, and all others were rejected. It will be noticed that the 

 temperature was gradually elevated about one degree each day during 

 the hatching process, and was maintained as nearly as possible to 77° 

 during the subsequent feeding state, the essential features of which are 

 presented in the following table. 



