96 piOGENESIS AND IIOMOGENESIS less. 



organisms, the theory of Biogenesis, according to which each 

 Hving thing, however simple, arises by a natural process of 

 budding, fission, spore-formation, or what not, from a parent 

 organism : and the theory of Abiogenesis, or as it is some- 

 times called Spontaneous or Equivocal Generation, accord- 

 ing to which fully formed living organisms sometimes 

 arise from not-living matter. 



In former times the occurrence of abiogenesis was uni- 

 versally believed in. The expression that a piece of meat 

 has " bred maggots " ; the opinion that parasites such as the 

 gall-insects of plants or the tape-worms in the intestines of 

 animals originate where they are found ; the belief still held 

 in some rural districts in the occurrence of showers of frogs, 

 or in the transformation of horse-hairs kept in water into 

 eels ; all indicate a survival of this belief. 



Aristotle, one of the greatest men of science of antiquity, 

 explicitly teaches abiogenesis. He states that some animals 

 "spring from putrid matter," that certain insects " spring 

 from the dew which falls upon plants," that thread-worms 

 " originate in the mud of wells and running waters," that 

 fleas " originate in very small portions of corrupted matter," 

 and that " bugs proceed from the moisture which collects 

 on the bodies of animals, lice from the flesh of other 

 creatures." 



Little more than 200 years ago one Alexander Ross, 

 commenting on Sir Thomas Browne's doubt as to " whether 

 mice may be bred by putrefaction," says, " so may he doubt 

 whether in cheese and timber worms are generated ; or if 

 beetles and wasps in cow's dung ; or if butterflies, locusts, 

 grasshoppers, shell-fish, snails, eels, and such like, be pro- 

 created of putrefied matter, which is apt to receive the form 

 of that creature to which it is by formative power disposed. 

 To question this is to question reason, sense, and experience. 



