I THALES TO LUCRETIUS 19 



animals, as of eels from the mud of ponds, and of 

 insects from putrid matter. However, in this, both 

 Augustine and Thomas Aquinas, and many men of 

 science down to the latter part of the seventeenth 

 century, followed him. For example, Van Helmont, 

 an experimental chemist of that period, gave a recipe 

 for making fleas ; and another scholar showed him- 

 self on a level with the unlettered rustics of to-day, 

 who believe that eels are produced from horse-hairs 

 thrown into a pond. 



Of deeper interest, as marking Aristotle's pre- 

 vision, is his anticipation of what is known as 

 Epigenesis, or the theory of the development of the 

 organism into the adult form among the higher 

 individuals by the division or segmentation of a 

 fertilised ovum or egg-cell. This theory, which 

 was proved by the researches of Harvey, the dis- 

 coverer of the circulation of the blood, and is 

 accepted by all biologists to-day, was opposed by 

 Malpighi, an Italian physician, born in 1628, the 

 year in which Harvey published his great discovery, 

 and by other prominent men of science down to the 

 last century. Malpighi and his school contended 

 that the perfect animal is already c preformed ' in the 

 germ ; for example, the hen's egg, before fecundation, 

 containing an excessively minute, but complete, chick. 

 It therefore followed that in any germ the germs of 

 all subsequent offspring must be contained, and in 

 the application of this ' box-within-box ' theory its 

 defenders even computed the number of human 

 germs concentrated in the ovary of mother Eve, 

 estimating these at two hundred thousand millions ! 



When the 'preformation.' theory was revived by 



