THE WONDER OF LIFE 575 



It is a grand piece of history beyond doubt the pre- 

 historic history of the organic world. If our conception 

 is right at all, there once was a time when the living creatures 

 of the Earth were very minute corpuscles of living matter 

 very simple but individuated, able to feed, grow, and 

 multiply, able to enregister their experiences. We must 

 try to think of them as simpler than any of the Protista 

 that are visible to-day. Perhaps the ultra-microscopic 

 Chlamydozoa may be nearest to them. 



Great Steps in Evolution. Looking backwards we 

 see a great succession of achievements. Within the realm 

 of the unicellulars we find every grade of structural differen- 

 tiation some relatively simple, some extraordinarily 

 complex like many of the Radiolarians. We can still 

 trace the gradual specialization of functions, the establish- 

 ment of the great types of cell life, the beginnings of repro- 

 duction and of death. One of the earliest steps was the 

 dichotomy which separated plants and animals the most 

 momentous cleavage in evolution. 



A simple instance may serve to bring out the point that 

 functions have become more specialized as evolution pro- 

 ceeded. W. Staniewiez has called attention to the interest- 

 ing fact that Protozoa have never learned to digest fat. 

 All multicellular animals have this power, but the Protozoa 

 have not. Experiments with Paramcecium, Stentor, 

 and some other common Infusorians show that fat may 

 be ingested, but it is not digested. It is not a natural 

 part of a Protozoon's food, and the fat that is occasionally 

 found in natural conditions within the Protozoon cell 

 seems to be due to the transformation of proteids or carbo- 

 hydrates. If the facts are correct, the power of digesting 

 fat was added on to the digestive function when the transi- 



