POPULAR SCIENCE. 5 



life. It was found that great diversity of type was discover- 

 able in the living beings that pervaded different substances, 

 and that each class of body revealed its own forms of life. 

 For example, the yeast fungus has been so frequently ob- 

 served and drawn, that microscopists now speak of it with 

 the same confident familiarity a botanist does of any variety 

 of the large field mushrooms. Again, the special form of 

 animal life to be met with in sour paste is that of an eel, and 

 under the guise of something like river eels they are to be 

 found depicted. Parallel cases need not be adduced to make 

 comprehensible the philosophic boundary we are arriving at. 



Out of revelations like these the question naturally 

 evolves itself: How came these things there? How came 

 the yeast fungus in yeast, the paste eels in paste ? and so on 

 for the rest. One of two hypotheses must be adopted as a 

 necessity. Either these living things must have been spon- 

 taneously generated, or must have been developed from some 

 kind of ovum, seed, or germ. As for the spontaneous-gene- 

 ration hypothesis, any general reader would most likely aban- 

 don it as absurd ; but this word ' absurdity ' is not lightly 

 adopted by the philosopher, whose usual and only legitimate 

 way of dealing with a disputed proposition is to take measures 

 by experiment, the issue of w T hich shall be to show the truth 

 or falsehood of the disputed phenomenon in question. Now, 

 improbable as the thing may seem, the idea of spontaneous 

 generation had, some few years ago, won to its side many 

 advocates amongst philosophers on the Continent, especially 

 in France; the evidence on which they based their hypo- 

 thesis being gathered from the fact that, notwithstanding all 

 care they had been enabled to take to insure fair conditions 

 of experiment, the living forms of decomposition, as, to gene- 

 ralise, we may call them, would and did present themselves. 

 It was found that the passage of air through such destructive 

 agents as oil of vitriol and potash solution did not interfere 

 with the development of these small forms of life. Flour- 



