XL] EVOLUTION IN BIOLOGY. 283 



of direct observations, that every living thing is 

 evolved from a particle of matter in which no trace of 

 the distinctive characters of the adult form of that 

 living thing is discernible. This particle is termed a 

 germ. Harvey 1 says 



" Omnibus viventibus primordium insit, ex quo et a quo pro- 

 veniant. Liceat hoc nobis primordium vegetale nominare ; nempe 

 substaiitiam quandam corpoream vitam habentem potentiH, ; vel 

 quoddam per se existens, quod aptum sit, in vegetativam formam, 

 ab interno principio operante, mutarl Quale nempe primordium, 

 ovum est et plantarum semen ; tale etiam viviparorum conceptus, 

 et insectorum vermis ab Aristotele dictus : diversa scilicet diver- 

 sorum viventium primordia." 



The definition of a germ as "matter potentially 

 alive, and having within itself the tendency to assume 

 a definite living form," appears to meet all the re- 

 quirements of modern science. For, notwithstanding 

 it might be justly questioned whether a germ is not 

 merely potentially, but rather actually, alive, though 

 its vital manifestations are reduced to a mini mum, 

 the term " potential " may fairly be used in a sense 

 broad enough to escape the objection. And the 

 qualification of "potential" has the advantage of 

 reminding us that the great characteristic of the germ 

 is not so much what it is, but what it may, under 

 suitable conditions, become. Harvey shared the be- 

 lief of Aristotle whose writings he so often quotes, 

 and of whom he speaks as his precursor and model, 

 with the generous respect with which one genuine 

 worker should regard another that such germs may 



1 " Exercitationes de Generatione." Ex. 62, " Ovum esse primor- 

 dium commune omnibus animalibus." 



