122 



THE ANIMALS AND MAN 



It is thus evident that the Protozoa are an ancient group 

 of animals. As a matter of fact zoologists are certain that 

 it is the most ancient of all animal groups. All of the animals 

 of the ocean depend upon the marine Protozoa and the 



marine Protophyta, 

 one-celled plants, for 

 food. Either they 

 feed on them directly, 

 or prey on animals 

 which in turn prey 

 on these simplest 

 organisms. A well- 

 known zoologist has 

 said: "The food-sup- 

 ply of marine ani- 

 mals consists of a 

 few species of micro- 

 scopic organisms 

 which are inexhausti- 

 ble and the only 

 source of food for all 

 the inhabitants of 

 the ocean. The sup- 

 ply is primeval as well as inexhaustible, and all the 

 life of the ocean has gradually taken shape in direct 

 dependence on it." The marine Protozoa are the only 

 animals which live independently; they alone can live 

 or could have lived in earlier ages without depending on 

 other animals. They must therefore be the oldest of 

 marine animals. By oldest is meant that their kind 

 appeared earliest in the history of the world, and as it 

 is certain that ocean life is older than terrestrial life that 

 is, that the first animals lived in the ocean it is obvious that 

 the marine Protozoa are the most ancient of all animal 

 groups. 



FIG. 48. Rosalina varians, a marine Proto- 

 zoan (Foraminifera) with calcareous 

 shell. (After Schultz.) 



