THE DAWN-ANIMAL AS A TEACHER IN SCIENCE. 217 



lud bituminous matter, resulting from the decay of 

 marine plants might accumulate in the sea-bottom. 

 Now arises the opportunity for animal life. The 

 plants have collected stores of organic matter, and 

 their minute germs, along with microscopic species, are 

 floating everywhere in the sea. Nay, there may be 

 abundant examples of those Amoeba-like germs of 

 aquatic plants, simulating for a time the life of the 

 animal, and then returning into the circle o£ vegetable 

 life. In these some might see precursors of the Pro- 

 tozoa, though they are probably rather prophetic ana- 

 logues than blood relations. The plant has fulfilled 

 its function as far as the waters are concerned, and 

 now arises the opportunity for the animal. In what 

 form shall it appear ? Many of its higher forms, those 

 which depend upon animal food or on the more com- 

 plex plants for subsistence, would obviously be un- 

 suitable. Further, the sea- water is still too much 

 saturated with saline matter to be fit for the higher 

 animals of the waters. Still further, there may be a 

 residue of internal heat forbidding coolness, and that 

 solution of free oxygen which is an essential condition 

 of existence to most of the modern animals. Some- 

 thing must be found suitable for this saline, imper- 

 fectly oxygenated, tepid sea. Something too is wanted 

 that can aid in introducing conditions more favourable 

 to higher life in the future. Our experience of the 

 modern world shows us that all these conditions can be 

 better fulfilled by the Protozoa than by any other 

 creatures. They can live now equally in those great 



