14 BASIC ASSUMPTIONS 



second view is that spontaneous generation occurred at some 

 finite time in the past but that it is no longer occurring. 



The continuous formation of life de novo. This theory is of 

 considerable antiquity and it might be as well to give a brief 

 resume of its history. The responsibility for it is usually placed 

 at the door of Aristotle. He wrote: " It is quite proved that certain 

 fish come spontaneously into existence not being derived from 

 eggs or copulation. Such fish as are neither oviparous nor 

 viviparous arise all from one of two sources, from mud or from 

 sand, and from decayed matter that rises hence as scum; for 

 instance the so-called froth of small fry comes out of sandy 

 ground. The fry is incapable of growing and of propagating its 

 kind, after living for a while it dies away and another creature 

 takes its place and so, with short interval excepted, it may be said 

 to last the whole year throughout." 



Other biologists gave various recipes for the formation of life 

 de novo. Virgil in his Georgics, Book IV, gives the recipe for the 

 formation of a swarm of bees from the barren carcass of a dead calf. 

 Van Helmont suggested that mice could be formed " if a dirty 

 undergarment is squeezed into the mouth of a vessel, within 

 21 days the ferment drained from the garment and transformed by 

 the smell of the grain, envelops the wheat in its own skin and 

 turns into mice." Van Helmont was surprised that mice formed 

 in this manner could not be distinguished from mice produced by 

 normal sexual breeding. 



The situation became more critical when the experimentalists 

 tried to determine whether it was possible to prevent living things 

 from appearing in preserved material. The experiments of 

 Needham, Pouchet and Bastian all indicated that living things 

 still appeared in solutions from which all previous life had been 

 removed, whilst Redi, Swammerdam, Vallisneri, Spallanzani, 

 Schwann, Pasteur and many others showed that if the experi- 

 ments were done very carefully it was possible to preserve soups, 

 blood or urine in an atmosphere of oxygen and still get no growth 

 of living material. It is not my intention here to discuss this old 

 controversy. Full and interesting details can be found in the books 

 of Oparin (1957), Singer (1950) and Wheeler (1939). Today 

 there are still people who think that living things of a high level 

 of complexity can be formed de novo. Of these it is perhaps of 



