48 PHYSIOLOGY OF THE EGGS 



presented by the eggs laid in the cocoon from which 

 the female has issued : 



I shall revert to this subject again, when treating 

 of Moths, and give examples of many peculiarities in 

 the different species, and of the manner in \vhich they 

 deposit their eggs. 



In reference to the degree of cold which the eggs 

 of insects can endure> I shall give the ingenious 

 experiments of John Hunter and Spallanzani on this 

 interesting subject. Indeed, the heat also which they 

 are capable of withstanding is not less astonishing. 



" Intense cold," says Spallanzani, " does not destroy 

 the eggs of insects. The year 1 709 was celebrated 

 for the intensity of its cold, and its fatal effects on 

 animals and plants. Fahrenheit's thermometer fell to 

 1. * Who can believe,' exclaims Boerhaave, ' that 

 the severity of this winter did not destroy the eggs 

 of insects, especially those exposed to its influence 

 in open fields, on the bare earth, or on the exposed 

 branches of trees ! Yet the general warmth of spring 

 having again tempered the air, these eggs were 

 hatched, and as numerously as in the mildest winters.' 

 Since that time, there have been \vinters still more 

 severe; for, in France, as well as in several other 

 European states, in December, 1788, the thermo- 

 meter fell considerably beneath that of 1709. 



