PKESIDKNTIAL ADDRESS. 43 



are greatly influenced by the environment, and, consisting en- 

 tirely as it were of reproductive cells, naturally transmit their 

 variations to their descendants directly. Only thus can vari- 

 abilit}^ be perpetuated, and whatever is true of them is true 

 of all germ-cells. "The origin of hereditary individual vari- 

 ability," says Weismann, "cannot indeed be found in the 

 higher organisms — the Metazoa and Metaphj-ta ; but is to be 

 sought for in the lowest — the unicellular organisms. In these 

 latter the distinction between body-cell and gerra-cell does not 

 exist. Such organisms are reproduced b}- division, and if, 

 therefore, any one of them becomes changed in the course of 

 its life by some external influence, and thus receives an indi- 

 vidual character, the method of reproduction ensures that the 

 acquired peculiarity will be transmitted to its descendants ' ' 

 (pp. 277-278). 



It is here that comes in his fundamental doctrine of the con- 

 tinuit}' of the germ-plasm. If not the germ-cells, at least the 

 germ-plasm of either parent passes intact to the offspring. It 

 is perpetual, or as he calls it, immortal. It gives to the new 

 being its special character, but receives nothing from it. It 

 remains in the offspring until it in turn becomes a parent, and 

 again passes to the third generation without ever having ceased 

 to live. Ever}' living being on the globe to-day contains in 

 its germ-plasm something that has never ceased to live since 

 the original life-breath was breathed into organic nature. 

 Through all the ancestral t3'pes of the phyletic chain it has 

 persisted, passing from parent to offspring through the trans- 

 forming series, so that in the loins of the highest types of man 

 there is something which was still living in the lowest primor- 

 dial worm and even in the bathybian ooze of those primeval 

 waters which in the earliest Cambrian times succeeded the 

 formation of the original crust of the globe. 



