ON THE ORIGIN OF DEATH. Ill 



differentiate to form the tissues and organs of the em- 

 bryo. Now of these cells in the embryo, Weismann 

 distinguishes two different kinds ; viz. the germ-cells 

 which lie in the generative glands of the animal, and 

 the somatic cells, which form all other organs and the 

 body itself. During early youth the germ-cells remain 

 dormant. When, however, adult life is reached, they 

 develop, and under proper conditions, such as fertiliza- 

 tion, etc., each one is capable of producing a new 

 organism, with germ-cells and body, while the body 

 itself grows old and dies. 



The germ-cells of the second generation do not die, 

 but produce a third, and the third a fourth generation, 

 and so on. The body of each of these generations must 

 grow old and die, but the germ-cells themselves, if 

 allowed the proper physical surroundings, do not. They 

 go on germinating, and so produce generation after 

 generation. 



Hence it would appear that the germ-cells of the 

 higher organisms are comparable to the entire body 

 of unicellular forms, and like them are endowed with 

 potential immortality ; and that this immortality has 

 never been broken by death since life has existed on 

 this earth. In other words, a Metazoon equals a colony 

 of Protozoa ////j" a perishable body. 



This theory he calls the '* continuity of the germ- 

 plasm." He compares the germ-plasm of the Metazoon 

 to the rhizome of a fern which runs along underground, 

 the perishable body to the green frond which grows up, 

 withers, and dies, without affecting the life of the 

 rhizome from which it springs. 



Death, then, is something secondary ; an ad^tation 



