SPONTANEOUS GENERATION. 303 



generations have been sufficiently numerous to 

 spread the species throughout a great part of 

 Europe. M. Hoogewerf showed a great flask full 

 to the Dutch biologists who met at Utrecht in 

 1 89 1. M. L. Errera presented others in June 1899, 

 to the Society of Medical and Natural Sciences at 

 Brussels. To-day the great manufactory of Sarg & 

 Co., of Vienna, is engaged in their production on a 

 large scale for industrial purposes. 



Thus we are able to study this crystalline species 

 of glycerine and to determine with precision the 

 conditions of its continued existence. It has been 

 shown that it does not resist a temperature of 18°, so 

 that if precautions were not taken to preserve it, 

 a single summer would suffice to annihilate all the 

 crystalline individuals existing on the surface of the 

 globe, and thus the species would be extinguished. 



Possible Extinction of a Crystalline Species. — As 

 these crystals melt at 18°, this temperature represents 

 the point of fusion of solid glycerine or the point of 

 solidification of liquid glycerine. But the liquor 

 does not solidify at all if its temperature falls below 

 18° C, as we well know, for it is at that temperature 

 we use it. Nor does it solidify at zero, nor even at 

 18° below zero ; at 20°, for instance, it merely thickens 

 and becomes pasty. We only know glycerine, then, in 

 a state of superfusion, a fact which chemists have not 

 learned without amazement. Under these conditions, 

 so analogous to the appearance of a living species, to 

 its unlimited propagation and to its extinction, the 

 mineral world offers a quite faithful counterpart to 

 the animal world. The living body illustrates here 

 the history of the brute body and facilitates its 

 exposition. Inversely, the brute body in its turn 



