20 Life and Death, Heredity and Evolution 



dead is found in the entire history of a race, save by accident. 

 The present living generation transforms directly into the 

 next one. Figure 5 illustrates the course of life and the 

 passage of generations in these creatures as compared with 

 that of higher organisms. 



All this is so different from what we ourselves experience 



Figure I. Division of an infusorian, Paramecium. Successive stages. 



and from what we see around us in the animals that we know, 

 that it has always aroused the greatest interest and led to 

 many questions. What ! are these creatures really im- 

 mortal? Is there no decline, no old age, no natural death 

 in their history? Does their life realize the dream of 

 perpetual youth? Such questions, as you know, were put 

 long ago by the early students of these creatures, and for 



