68 The Outline of Science 



cells, showing division of labour. There are some other Protozoa 

 in which the nucleus or kernel divides into many nuclei within the 

 cell. This is seen in the Giant Amoeba (Pelomyxa), sometimes 

 found in duck-ponds, or the beautiful Opalina, which always lives 

 in the hind part of the frog's food-canal. If a portion of the 

 living matter of these Protozoa should gather round each of the 

 nuclei, then that would be the beginning of a body. It would 

 be still nearer the beginning of a body if division of labour set 

 in, and if there was a setting apart of egg-cells and sperm-cells 

 distinct from body-cells. 



It was possibly in some such way that animals and plants 

 with a body were first evolved. Two points should be noticed, 

 that body-making is not essentially a matter of size, though it 

 made large size possible. For the body of a many-celled Wheel 

 Animalcule or Rotifer is no bigger than many a Protozoon. Yet 

 the Rotifer we are thinking of Hydatina has nine hundred 

 odd cells, whereas the Protozoon has only one, except in forms 

 like Volvox. Secondly, it is a luminous fact that every many- 

 celled animal from sponge to man that multiplies in the ordinary 

 way begins at the beginning again as a "single cell" the fertilised 

 egg-cell. It is, of course, not an ordinary single cell that develops 

 into an earthworm or a butterfly, an eagle, or a man ; it is a cell 

 in which a rich inheritance, the fruition of ages, is somehow con- 

 densed ; but it is interesting to bear in mind the elementary fact 

 that every many-celled creature, reproduced in the ordinary way 

 and not by budding or the like, starts as a fertilised egg-cell. The 

 coherence of the daughter-cells into which the fertilised egg-cell 

 divides is a reminiscence, as it were, of the primeval coherence of 

 daughter-units that made the first body possible. 



The Beginning of Sexual Reproduction 



A freshwater Hydra, growing on the duckweed usually 

 multiplies by budding. It forms daughter-buds, living images 

 of itself; a check comes to nutrition and these daughter-buds go 



