LIFE IN THE PRIMITIVE OCEAN 33 



precisely opposite development from that of the plant. 

 It means "hunting"; so the hunter and the hunted 

 develop, very gradually, organs of locomotion, sense- 

 spots, mouths, stomachs, weapons, armour, etc. 

 Even in the microscopic life of the pond, where every 

 organism is still a single cell, you get bewildering 

 variety of developments of this kind. But we cannot 

 linger here over this stage. 



In tim.e the cells cling together, and larger animals 

 ("man^^-celled") are formed. This affords a better 

 opportunity for specializing. Some cells become 

 muscle-cells, some nerve-cells, some stomach-cells, 

 some weapon-cells, and so on. You can see all this 

 in a primitive way, under the microscope, in the 

 common pond hydra. The jelly-fish or the anemone 

 you find at the coast are advances of the same type. 

 The animals grow larger and larger, and the develop- 

 ment of their separate parts increases. Eyes and 

 other senses begin as little pits in the skin lined with 

 sensitive cells, and slowly improve. After a time (in 

 lowly worms) these are connected with each other and 

 with a group of nerve-cells in the head : the primitive 

 brain. 



¥7hat I have described in the last four paragraphs 

 certainly took millions of years, and probably tens of 

 millions of years ! During all that time animals were 

 soft-bodied, and have left no ''fossils." It is by 

 studying them in nature to-day that we trace the 

 lines of their evolution. But at last animals with 



