84 BIOLOGY 



CHAPTER XVI 



OLD AGE AND DEATH 



IT seems fitting to draw this brief account of Biology 

 to a close with a few remarks on the subject of Old 

 Age and Death. 



We are accustomed to think of living organisms as 

 mortal, and it is difficult to tear ourselves away from 

 this belief. Laving things, it is true, are mortal, but 

 the germ-plasm is immortal and continuous. 



Many of the uni-cellular organs whose multiplication 

 takes place by fission escape old age and death, as the 

 whole body of the parent is divided between the off- 

 spring. It is also said that in the conjugation of many 

 of the uni-cellular forms there is a rejuvenescence of the 

 protoplasm, and therefore a warding off of death. When 

 the sexual mode of reproduction is reached, the condi- 

 tion of things is altered but little, for the sexual cells 

 mingle at least part of their protoplasm during fertilisa- 

 tion, and the resulting cell, or fertilised ovum, forms the 

 starting point of a new generation, and pervades the 

 whole soma thereof, and so the germ-plasm is handed 

 down from generation to generation. 



It is undoubtedly true that the individual organism 

 which gives rise to the germ-cell may die, but that is 

 only the death of the cells that have grown up round 

 the germ-plasm for the purpose of protecting and 



