CH. LIX.] THE CYCLE OF LIFE 861 



of charitable endeavours is in itself a sign of progress ; it indicates 

 a growth of the feelings of compassion and unselfishness which con- 

 stitute a great asset in the possessions of a race. The laws of evolu- 

 tion operate in spite of artificial hindrances ; this is exemplified in 

 what is termed the law of anticipation ; by this is meant that in a 

 heritable disease its effects develop at an earlier and earlier age in 

 successive generations, until at last it causes death at a period 

 before the sexual organs attain maturity, and thus automatically its 

 continued propagation is put a stop to. 



In a simple unicellular organism such as the amoeba, there is not 

 only no differentiation of sex, but there is also no differentiation 

 between the reproductive element (Weismann's germ plasm) and 

 the remainder of the body (Weismann's somatoplasm). When the 

 amoeba propagates itself by dividing into two new amoebae, the 

 whole animal is concerned in the act of reproduction, and, barring 

 accidents, the new amoebae may behave in this way indefinitely, and 

 so may be spoken of as immortal. In this sense the only part of 

 the body which is immortal (in the material as opposed to the theo- 

 logical use of the word) in the higher animals is the germ plasm, 

 which lives beyond us to repeat the process an infinite number of 

 times in our descendants. 



If now we deal in a more matter-of-fact way with the present 

 instead of the past or the future, the faculty which living organisms 

 have of reproducing themselves furnishes us with a new conception 

 of the life process. The common lot of all is to die, and life in the 

 individual is then extinct ; but each individual is only a link in a 

 long chain of lives, and life is thus not something which begins and 

 ends like & straight line ; it is rather to be compared to a circle, in 

 which a series of events is repeated over and over again. If we 

 start with the ovum we are led to the foetus, and then to the child, 

 and the adult who produces or fertilises an ovum once more ; and 

 so history goes on repeating itself. 



I propose, however, in the following account of some of the 

 details of the long story, to start at a different point in the cycle. 

 We will take first the new-born child, and rapidly run through what 

 occurs after its birth until the state of sexual maturity is reached. 

 Next it will be our duty to consider the structure and physiology 

 of the reproductive organs, and how the ova in one sex, and the 

 spermatozoa in the other sex, originate. Next will follow an account 

 of the union of these reproductive cells, and the production of a 

 fertilised ovum. This will be followed by a brief account of the 

 development and life of the foetus, until we reach the mechanism by 

 which the new-born child is expelled from the uterus into the world, 

 which will bring us back to the point from which we started. 



