THE ORIGIN OF LIFE 97 



lower organisms later on in a more detailed manner. We shall 

 then see that unicellular animals and plants are not by any 

 means primitive but highly complex organisms, and that even 

 the lowest bacteria and protozoa whose structure the micro- 

 scope has revealed to us bear such distinct vestiges of a long 

 historical development that it is impossible to regard them as 

 owing their existence to spontaneous generation. 



When we ask ourselves how those organisms would be con- 

 stituted that might have been ' crystallized ' from inorganic 

 matter, the only answer which sound reason can find is that they 

 must stand on the lowest conceivable step of organic life. We 

 shall agree with Ernest Haeckel, the great but dogmatic pro- 

 tagonist of the theory of descent, " that the organisms that came 

 into existence by spontaneous generation were not cells at all, 

 but perfectly homogeneous, structureless, amorphous lumps of 

 albumen." But all organisms, animals as well as plants, w^hich 

 are known to-day show structures, and differentiations in their 

 structures, and have, therefore, apparently reached the stage of 

 cells. On the ground of Pasteur's experiments and these con- 

 siderations we seem, therefore, justified to infer that for all these 

 organisms the old saying applies : Omni vivum e vivo. 



But are we now entitled to deny the possibility of a genera- 

 tion without ancestors? I am inclined to answer, No. It is 

 true that the perfection of optical instruments has unlocked 

 a whole world of life of which former generations had no con- 

 ception. Our microscopes, with a power of magnifying 3,000 

 times, enable us to perceive organisms so minute that they far 

 transcend our power of imagination, and yet we know that the 

 last boundary of the infinitely small is as yet far off, and that 

 there exists life which lies beyond the present limit of our 

 senses. Indeed, in order to prove the existence of many 

 organisms which singly are too minute to be made visible we 

 are compelled to offer them in suitable artificial nutrient media 

 an opportunity for enormous multiplication, so that they may 

 betray their presence by the clouding of the medium, or by 

 other signs. Of their structures, however, whether they are 

 cells or structureless lumps of albumen, we know nothing. 

 Whether such organisms originate to-day is a question which lies 

 where experience ceases and faith begins. A number of years 

 7 



