SEX IN LIVING FORMS 73 



Spontaneous Generation.— By this term is meant 

 the supposed formation of living creatures directly 

 from dead matter without the intervention of other 

 living organisms. The theory is, in substance, an old 

 one. The ancients supposed that the frogs and other 

 small reptiles so abundant in the vicinity of slimy pools 

 and stagnant marshes, were generated spontaneously 

 from the mud and slime in which they lived. This 

 theory was, of course, abandoned when the natural 

 history of reptiles became known. 



For several thousand years the belief was still held 

 that maggots found in decaying meat were produced 

 spontaneously; but it was discovered, centuries ago, 

 that maggots are not formed if the flesh is protected 

 from flies, and hence must be the larvas of a species 

 of this insect. A relic of the ancient belief in sponta- 

 neous generation is still found in the supposition that 

 horse-hair snakes, so-called, are really formed from the 

 hairs of horses. This belief is quite common, but science 

 long ago exposed its falsity. It is now known that the 

 horse-hair snake is a parasitic worm, which spends 

 part of its existence in the stomach of a certain species 

 of beetle. After beginning its independent existence, 

 it frequents moist places, such as stagnant pools by the 

 road-side, watering troughs, etc. '\^'Tien the water dries 

 up, the horse-hair snake becomes dry and apparently 

 lifeless, and shrivels up, so that it is not readily dis- 

 covered. A new rain moistens the little creature, and 

 brings it into active life again so suddenly that it seems 

 like a new creation, or, according to the popular opin- 

 ion, appears to be converted from a dead hair into a 

 living snake. 



Germs.— When the microscope was discovered, it 

 revealed a whole new world of infinitesimal beings. 



