THE ORIGIN OF LIFE. 35 



living matter has been studied it has been believed 

 by many that living organisms could arise spon- 

 taneously, i.e.j without having any direct living 

 ancestors. Aristotle held this view, and from his 

 time for centuries no one presumed to doubt that 

 most of the smaller organisms could, and usually did, 

 arise spontaneously. It was not until the sixteenth 

 century that the matter became one of discussion. 

 At that time Redi discovered that fly-maggots were 

 not produced spontaneously from decaying flesh as 

 had hitherto been believed, but came from some- 

 thing deposited by adult flies. This discovery led 

 him to further observation, and finally to the con- 

 clusion that there was no such thing as spontaneous 

 generation. Since that time this doctrine has been 

 the ground of many a hard-fought battle. The fol- 

 lowers of Redi speedily began to show by careful 

 study of the facts that numerous cases of so-called 

 spontaneous generation were simply due to careless 

 observation. It was soon proved that at least all 

 the higher animals arise by the method of reproduc- 

 tion only. The adherents of the belief that life can 

 arise from the non-living were thus driven to base 

 their claims upon the origin of the smaller organ- 

 isms, and finally upon microscopic forms, which 

 can be studied only with extreme difficulty. But 

 so far from admitting this to be a retreat from their 

 position, they have shown that it is the most natural 

 conclusion possible. For a priori grounds should 

 serve to convince us that if living things can arise 

 from the non-living, this would be true only of the 

 very lowest organisms, those which approach the 



