30 THE SIMPLEST FORMS OF LIFE 



alone at a much lower level of organisation ; and nearly a 

 thousand species of vegetal organisms that equally consist 

 of a single cell or something less than a cell. It is the dis- 

 covery of this vast world of simple microscopic beings that 

 has made spontaneous generation more conceivable. The 

 famous experiments of Pasteur, which uninformed writers 

 still confusedly quote in this connection, related to organisms 

 with a locomotor apparatus and a degree of sensitiveness 

 that lift them to a much higher place in the animal hierarchy. 

 If the first living things to appear on our earth had been 

 infusoria, we might more reasonably entertain Lord Kelvin's 

 idea of the arrival of germs from other planets, or the theo- 

 logical theory of creation ; though even then it is not clear 

 how Sir Oliver Lodge's theory would help us. But we have 

 hundreds of species below the level of the infusoria, and we 

 may be quite confident that when we regard these we are 

 nearer to the original inhabitants of our oceans. 



Why may we be so confident, when we acknowledge that 

 we have no remains preserved of these primitive organisms ? 

 There is no dispute about the point in biology, but it is 

 worth while pointing out the grounds. One reason is in the 

 general law of evolution. Apart from a comparatively small 

 number of degenerate parasites (especially among worm-like 

 creatures), the story of life runs from the simpler forms to the 

 more complex. Since this has been the absolute rule among 

 the preserved specimens, we have a right to suppose it held 

 good before the fossil stage began. Further though all 

 biologists would not use this argument all animals and plants 

 now begin their existence in the form of a simple microscopic 



