SPONTANEOUS GENERATION 215 



be produced from the decomposing body of a dead ox affords a 

 very striking illustration of that want of scientific training in 

 observation and reasoning which has led to so many erroneous 

 beliefs. He tells us, with much elaboration of detail, that if the 

 body of an ox is well beaten and enclosed in a suitable chamber a 

 swarm of bees will arise from it within a certain number of days. 

 We now know perfectly well what may really happen under these 

 circumstances. In the first place the supposed bees are not bees 

 at all, but drone-flies, which superficially resemble bees, though 

 easily recognizable as belonging to a totally different order of 

 insects by the fact that they possess only two wings instead of 

 four, and consequently any husbandman who followed Vergil's 

 instructions must have been grievously disappointed in his 

 expectations of honey. In the second place the drone-flies are not 

 spontaneously generated from the body of the ox, or from any- 

 thing else, but are hatched out, first in the form of maggots, from 

 eggs which were laid by pre-existing flies. These maggots, 

 .having fed abundantly on the decaying carcase, presently undergo 

 their metamorphosis and emerge as flies. 



Many similar instances of alleged spontaneous generation, all 

 resting upon gross ignorance of the real facts of the case, might 

 be collected from the writings of ancient and mediaeval authors. 

 The cruder stories, which could be easily disproved by simple 

 observation, were soon cast aside as fables under the influence of 

 modern scientific methods. The invention of the microscope, 

 however, and the consequent revelation of a new world of 

 hitherto invisible organisms, led to a revival of the doctrine of 

 abiogenesis. It was noticed that organic infusions, even after 

 boiling, presently became densely filled with various kinds of 

 micro-organisms, especially Bacteria, and as the boiling was 

 supposed to have killed any organisms that might have been in 

 them at first it was argued that living things arose in them 

 de novo, by spontaneous generation. This was, however, merely 

 a revival of Vergil's story of the swarm of bees in a more refined 

 form. Had Vergil's ox been protected from flies none of the 

 alleged bees would have been produced, and the careful experi- 

 ments of such observers as Tyndall and Pasteur have conclusively 

 demonstrated that if the organic infusions are adequately pro- 

 tected from the countless microscopical germs which float in the 

 air they will remain free from living organisms, and consequently 

 from putrefaction, for an indefinite period, provided always that 



