EFFECTS OF COLD UPON EGGS. 97 



are so penetrated and frozen by the cold, that their 

 members do not yield to the pressure of the finger, 

 and seem perfect ice under the knife. This does 

 not happen to eggs, though subjected to cold of much 

 greater intensity. Their contents remain fluid, even 

 at the greatest cold, as may be seen by crushing them 

 with the nail. Perhaps this is derived from constitu- 

 ent spirituous or oleaginous parts, or from some prin- 

 ciple adapted to abate the power of cold.* If eggs 

 do not freeze, it is probable the included embryos do 

 not freeze. Is there anything wonderful, therefore, 

 that they then survive cold which is fatal to them 

 when produced ? Probably for the same reason (and 

 I see no objection that can apply), animalcula, con- 

 centrated in the germ, can support a degree of cold 

 they are incapable of when developed. 



' As the temperature of freezing still retains a 

 portion of heat, why, it may be asked, should it not 

 develope the germs of the most minute animalcula? 

 Had we never seen any eggs hatched but those of 

 birds, which require 104°, we should have concluded 

 that all others require the same. A little initiation 

 into the study of minute animals teaches how many 

 kinds produce at a temperature infinitely less. Such 

 are the eggs of butterflies and many other insects, of 

 frogs, lizards, tortoises, down to some, as those of 

 toads, which I have seen produce at 45°. If these 

 eggs hatch at 59° less than is required by those of 

 birds, what repugnance will there be to suppose that 

 at 13° less, or the freezing point, the eggs of other 

 animals may be hatched ? Nor should it surprise me 

 to be told of animals whose eggs would produce at 

 much greater cold, after knowing that there are plants, 

 beings so similar to animals, and many of them, 



* In piain language, Spallanzani did not know what to 

 make of the facts. 



