THE CONCEPTION OF LIFE IO9 



astronomers had asserted the evolution of our planetary 

 system, after the geologists had asserted the evolution of the 

 world, followed Darwin, who convinced us of the necessity of 

 assuming the evolution of plants and animals. Evolution 

 leads us back to a time when the conditions. on our earth were 

 such that Ufe, as we now know it, must have been impossible. 

 Life appeared later. It is therefore clear that somehow living 

 substance must have arisen on the earth. Thus it became an 

 intellectual necessity for us to assume in this sense the spon- 

 taneous generation of hfe. Those who make this assumption 

 have, strictly speaking, only one explanation to offer, namely 

 the supposition that proteid molecules could be formed, under 

 the then prevaiUng conditions, and by chance so come together 

 and unite in combination with other substances that they 

 would produce the first living substance. If we may venture 

 to pass judgment on this hypothesis we must bear in mind 

 that it is merely the expression of our desire to meet the 

 assumed needs of the doctrine of evolution. The h3rpothesis 

 has no further real scientific foundation. Pfliiger^^ has 

 endeavored in a clever and interesting memoir to determine 

 speculatively the possibility of the origin of proteid sub- 

 stances, but he did not get beyond speculation. To be exact, 

 we must consider that we have reached the new doctrine of 

 spontaneous generation through our inabihty to conceive the 

 origin of life otherwise. I imagine a very interesting and 

 instructive book, which is to be on the theme how often the 

 scientific man has been led to false conclusions through the 

 assumption "it must be so because we cannot conceive it 

 otherwise." We may never say in science, it is impossible. 

 The time of scientific surprises is not over. A few years ago, 

 physicists thought that they had already discovered the basic 

 phenomena of their science, and yet they are all today occu- 



