CHAPTER ONE. 

 THE CIRCLE OF LIFE. 



1. Why Do We Call It a Circle? If you stop to think 

 of life on the earth as you have seen it year after year, 

 you realize that it changes very little. This is true whether 

 we speak of the life of mankind or of all life of every kind. 

 There is just about so much grass on the lawn, about so 

 many weeds in the fence rows, about so many insects in 

 the air during one year as another. There are just about 

 as many babies and children and young people and middle- 

 aged folks and old people and those who are passing away 

 at one time as at another. Yet we know that all of us are 

 growing older all the time. Life keeps up a procession in 

 the same direction, and yet does not get any place, or at 

 least seems to be continually getting round to the same 

 place. This sounds like a circle, but the term is rather 

 misleading. We know very well that it is not the middle- 

 aged people who themselves come back and start life over 

 again. It is a new generation that continually follows the 

 old. On account of this seeming recovery of life in the 

 face of universal deaths, we call the course of life a circle 

 or cycle. A given individual does not come back to the 

 starting place, but the race is always being renewed by 

 new, young individuals. 



2. What Events Compose the Circle? If then we 

 overlook the fact that there is no real circle, let us see 

 what are the principal points in this seeming round of life. 

 You know that all plants and animals come into life very 

 small and helpless. They go through a time of rapid 

 growth, which in humans we call childhood and youth. 

 After a time they become mature. Then, for a while, in 

 middle-life, they just about hold their own. Gradually 

 they show signs of old age, and decline, and later die. 

 This is true of practically all individuals of every kind of 

 plant and animal. Some of them have very short periods, 

 lasting a few days or weeks. Many plants go through all 

 these stages in a year. Still others require centuries or 

 even thousands of years to pass from the beginning to 

 the end of life. 



3. The Beginnings of Life. No one knows anything of 

 the actual beginnings of life on the earth, but we all have 

 seen the young bean seedling coming out of the seed, the 

 young tadpole just out of the egg, the young chicken just 

 hatched, or the young calf or puppy recently born. This 

 is not really the beginning of life for any one of these, 

 because if they had not been living before sprouting or 

 hatching or being born, these things would never have 

 happened to them. For our present purposes, however, 

 this may be taken as the beginning of the individual. In 

 some way there is in this young plant or animal all the 

 possibilities of the adult. If the conditions are right it 

 will go on day by day adjusting itself to these conditions 

 and will come to be pretty much what its parents were. 



4. Growth. Growth is increase in size. There may be 

 other changes in connection with growth, but growth is 

 just this and nothing more. Living things grow by taking 

 up water and stretching the old parts, or by taking up 

 foods of various kinds and building up some new parts. 

 Growth seems a rather simple thing. It is, however, very 

 complex, and it is quite different in different living things. 



In most higher plants the growth occurs only at certain 

 definite points. The growth is local. The growing points, 

 where the cells use the water and foods and thus grow 

 and form new cells, are usually at the tips of the twigs 

 and roots and in a thin shell about the plant, beneath the 

 bark. The inner, older parts of the plant become hard and 

 rigid, and lose their power of growing. 



It is somewhat different in most animals. They grow 

 as the little pig which "died in clover," that is to say they 

 grow "all over." In them all the cells, with some 

 exceptions, divide and grow. There are no special regions 

 of growth. 



With all the differences in growth, however, all growth 

 is alike in that it is due to the fact that some of the cells 

 take in water and foods, and expand. These cells may 

 divide many times and continue to expand after each 

 division. 



5. Immaturity. The period of growth comes early in 

 life in those organisms that grow all over. Presently it 

 ceases. In those whose growth is local, it continues 

 throughout life, but it is always in the youngest parts. 

 Growth is thus always a sign of immaturity. During 

 growth the upbuilding processes are more powerful and 

 rapid than the destructive. The length of the growth 

 period in plants and animals differs as much as the length 

 of life itself. These periods correspond in length. If the 

 whole life period of an animal is long, its immaturity is 

 likely to be long; if the youth is short, the life is likely to 

 be short. 



Organisms frequently pass through striking changes in 

 appearance during this period of immaturity. The word 

 larva suggests some of these. The immature (larval) 

 butterfly is not like a butterfly, but is a worm-like 

 caterpillar; the immature frog does not look like the adult, 

 but has a tail and gills, as a fish has. The leaves of the 

 seedling plant are very different from those of the old 

 plant. This period is very important in many other 

 organisms beside man. It is the formative period. The 

 expression "as the twig is bent the tree inclines," expresses 

 a general law of life. The growth period is the great time 

 of adjustment. It is the period in which the plastic 

 individual gets a chance to work out its adjustments to 

 the important conditions of its life. 



6. Maturity. At maturity a plant or animal comes to its 

 full powers, size, and nature. At this stage the increase 

 is no longer greater than the outgo. They just about 

 balance. The length of time that this is true also varies 

 greatly in different kinds of organisms. Some begin to 

 decline in a few days or weeks after becoming mature. 

 This is true of a great many insects. In others there may 

 be a mature period of a great many years, as in the various 

 trees or in the larger animals. In man full maturity lasts 

 about fifteen or twenty years; that is, from thirty years of 

 age to forty-five or fifty. These figures are somewhat 

 misleading, inasmuch as some of our qualities may not 

 reach maturity by thirty, and others begin to wane before 

 we reach thirty. 



7. Decline and Old Age. We may think that old age 

 is just a matter of time. A little thought, however, will 

 convince you that this is a very small part of the story. 

 A grasshopper or a mouse "grow old" while a child or 

 a colt of the same age is still young. It is not primarily 

 time but something within which makes old age, and the 

 decline in power that comes with it. In some way the 

 aging plant or animal cannot continue to adjust itself to 

 the conditions about it. This adjustability to conditions 

 we find to be the real essence of life. For a while 

 the individual meets fully and profits by the surrounding 

 conditions. It receives stimuli, responds to them, and 

 becomes better because it does this. It learns, so to speak, 

 how, through its experiences, to adjust itself the better. 

 Thus it grows, matures, thrives. After a time, perhaps it 

 loses some of its plasticity or softness, its tissues harden, 

 its habits harden, and it no longer meets all its changing 

 needs so well. 



Then, too, it may be that all organisms, and all the cells 



