A CQ UIRED CHAR A CTERS 



as Nageli can forget its claims, and believe himself entitled 

 to draw conclusions as to the evolution of organic nature from 

 cultivation experiments, carried out during a few years with 

 negative result, and to deduce from them a " fixed law." 



Yet more : it is only a few years since we have reached 

 the conviction that the Egyptian civilisation stretches back 

 more than 6000 years behind us. A few years ago, after Darwin 

 had proposed his theory of the origin of species, his conserva- 

 tive opponents believed themselves justified in urging against 

 the doctrine of the modifiability of species, that the species 

 of cereals and other plants and also animals known from the 

 ancient Egyptian times had not changed up to the present 

 day, for the period of time in question seemed to them 

 eternal. The Darwinians explained in reply that demon- 

 strably the external conditions have not changed in Egypt 

 since that time, and that therefore in the particular case no 

 inducement, no necessity has existed for the new adaptation 

 of the living beings, and therewith for their modification. 

 But quite recently Weismann employs the fact cited by 

 Darwin's opponents to prove that the germ -plasm is a 

 substance of extreme power of persistence, a substance, he 

 says, "which is nourished and grows to an enormous ex- 

 tent without changing thereby in the slightest degree its 

 complicated molecular structure. We ought," continues 

 Weismann, " to maintain this with all certainty, like Nageli, 

 although we can get no direct perception of this structure. But 

 when we see that many species have reproduced themselves 

 for thousands of years without change I mention merely the 

 sacred animals of ancient Egypt, whose embalmed bodies 

 must in some cases be 4000 years old this proves to us that 

 their germ-plasm possesses still to-day the same molecular 

 structure which it had 4000 years ago. And since, further, 

 the amount of germ-plasm which is contained in a single 

 germ- cell must be supposed very small, and since of this 



