46 EVOLUTION AND DOGMA. 



Even so late as the last century, there were 

 learned men who did not hesitate to declare that 

 mussels and shell-fish are generated from mud and 

 sand, and that eels are produced from dew. 



Redi's Experiments. 



The first one effectively to controvert the doc- 

 trine of abiogenesis was Francesco Redi, of the cele- 

 brated Academia del Cimento, of Florence. In his 

 remarkable work entitled " Esperienze intorno alia 

 Generazione degl' Insetti," published in 1668, he dis- 

 tinctly enunciates the doctrine that there is no life 

 without antecedent life omne vivum ex vivo that all 

 living organisms have sprung originally from preexist- 

 ing germs, and that the apparent production of or- 

 ganized beings from putrefied animal matter, or vege- 

 table infusions, is due to the existence or introduc- 

 tion of germs into the matter from which such beings 

 seem to originate. 



The experiments by which Redi proved his as- 

 sertion were as simple as they at the time were con- 

 clusive. 



He placed some meat in a jar and then tied 

 fine gauze over the top of the jar. The meat 

 underwent putrefaction but no maggots appeared. 

 Redi hence inferred that maggots are not generated 

 by decomposing meat, but by something which is 

 excluded from the jar by the gauze. He soon dis- 

 covered that this something which had eluded all 

 previous observers, was the eggs of a blow-fly, which, 

 when deposited on meat, or dead animals, invariably 

 gave rise to the maggots that had hitherto been 



