52 FOUNDATIONS OF BIOLOGY 



But during bacterial ascendency another factor has been 

 gradually intruding itself almost imperceptibly into the 

 drama. This is the microscopic animal life which has 

 been multiplying with increasing rapidity as conditions 

 became more favorable, and forthwith assumes the dominant 

 life phase in the infusion. Among the animal forms, the 

 first to appear are exceedingly minute flagellated Protozoa, 

 known as Monads, many species of which absorb products 

 of organic disintegration brought about by the Bacteria, 

 while others ingest solid food the Bacteria themselves. 

 Then tiny ciliated animals, close relatives of Paramecium, 

 appear in untold numbers and feed upon the Bacteria. The 

 dominance of these smaller ciliates is brought to an end 

 after a few days by the ascendency of larger ciliates, which, 

 though feeding to a certain extent upon the already greatly 

 depleted bacterial population, obtain most of their food by 

 eating the smaller ciliates. And so the cycle of life continues 

 saprophytic forms gradually being replaced in dominance 

 by herbivorous and these in turn by carnivorous organisms. 



But obviously this chain of events must sooner or later 

 come to an end through the dissipation of energy brought 

 about by the metabolic processes of the colorless plants and 

 animals. Sooner or later the supply of potential energy 

 stored up in the chemical compounds of the hay will have 

 become nearly or completely exhausted transformed 

 into the kinetic form and expressed in the life activities of the 

 plant and animal population. 



Thus, after a few weeks, the hay infusion world has reached 

 a standstill extermination faces the population and 

 inevitably occurs unless microscopic green plants, possibly 

 Sphaerella, find their opportunity to develop in the energy- 

 exhausted environment and proceed to entrap the kinetic 

 energy of sunlight, store it up in carbohydrates and proteins, 



