INTRODUCTORY PROBLEMS 3 



the most essential difference is. The teacher who knows his 

 business will certainly not trouble the young mind with attempts 

 at defining life ; but, as a real acquaintance with living creatures 

 grows wider and deeper, he may help the pupils to feel more 

 vividly and precisely that plants and animals have more in 

 common with them than stones or clouds or machines have. He 

 may help the senior pupils to feel the difficulty of arriving at any 

 sort of idea of what livingness means. The following summary 

 may be found useful. 



(a) From the Biologist's Point of View. Living creatures have 

 the power of growing, of growing not as a snowball grows, but by 

 a unifying incorporation; nor even as a crystal grows, at the 

 expense of dissolved material chemically the same as itself, but 

 at the expense of material quite different from itself. The grass 

 grows at the expense of air, water, and salts, which, with the 

 sun's help, it lifts into the circle of life, and at the expense of 

 the grass the weaned foal grows into a horse. [Show the growth 

 of a crystal of alum. Contrast different kinds of food.] 



Another characteristic of living creatures is their cyclical 

 development. The germ of a plant or animal develops quickly 

 or slowly into an adult ; this gives origin to new lives, and then 

 there is a quick or slow down-grade ending in death. Out of the 

 apparent simplicity of the embryo the obvious complexity of 

 the full-grown creature develops; but, as Huxley put it, "no 

 sooner has the edifice, reared with such exact elaboration, at- 

 tained completeness than it begins to crumble. " We find not- 

 living things passing from one form to another the water 

 vapour gathering around dust-particles becomes mist, which 

 rises into a cloud, which is dissolved in raindrops, which freeze 

 into hailstones, which melt into water, and so on ; but in the 

 development of the living creatures there is orderly progress, 

 in part regulated from within, and there is a continuation of the 

 race though the individuals die. [Arrange a series showing 

 transformations in not-living things, e.g. vapour, fluid, solid 

 forms of the same substance. Arrange a series showing the 

 development of a plant or animal, e.g. seed, seedling, sapling, 

 flowering branch ; or, the life-history of a butterfly or beetle. 



