158 LECTUEES ON BIOLOGY 



vegetables when observed individually exhibit undoubtedly a 

 surprising fitness, but we see a different picture when we regard 

 them as a whole. The large majority of animals are herbivorous ; 

 day after day they destroy enormous quantities of nourishing 

 plant life in order to exist. To the plant kingdom, therefore, the 

 existence of herbivorous animals represents the very extreme 

 of unfitness. The vegetarian animals again serve as food for 

 the great number of carnivorous animals, and from their point 

 of view the existence of the flesh-eaters is most undesirable. 

 Even if we take up a purely anthropocentric position and regard 

 man as the measure of all things and the final aim of creation, 

 and assume that everything has been created for his purposes 

 we cannot, even in that case, escape from contradictions. For 

 what fitness is there in the fact that intestinal parasites, trichinae, 

 fleas, bugs, and mites, as well as the enormous armies of bacteria 

 and parasitic protozoa, are so perfectly adapted for their parasitic 

 mode of life that they scorn all medical art, torment the ' lord 

 of creation,' and exact each year a toll of millions of human 

 lives ? Is it not rather blasphemy to assume that an all-loving, 

 all-powerful Creator had designed the animal and vegetable 

 plant world so perfectly only to let them loose against each 

 other in a fierce relentless struggle ? 



Finally, whilst, generally speaking, the structure of organisms 

 is well adapted to the conditions of life, it is far from perfect, for 

 we have already met in man organs which actually endanger 

 his life. 



It is Darwin's great merit that he for the first time directed 

 the attention of the scientific world to the enormous waste of 

 life and discovered in this apparently blind play of chance a 

 deeper reason. The theory of the struggle for existence and 

 the doctrine of a natural selection of the fittest in this struggle 

 enables us to explain the origin of numerous adaptations in 

 nature mechanically, that is, naturally, without being driven 

 to the assumption of a supernatural Creator. Whether Dar- 

 win's hypothesis suffices in all cases is another question which 

 we shall have to examine later. But whatever the decision 

 may be, it must be clear that the validity of the theory of 

 selection can only affect a relatively unimportant problem of 

 organic life, for to the first and foremost question, the riddle 



