4 LIFE S BEGINNING ON THE EAETH 



organization adequate to meet the requirements for their 

 existence have disappeared from the earth. This is why we 

 see nothing but purposefulness in life. This statement 

 seems to be so self-evident that it hardly requires further 

 elucidation. The puzzling feature, however, is the bound- 

 less variety of the forms of life we see around us. 



How can we hope to account for this variety? A thought- 

 ful student of nature finds an answer by considering all 

 living things as documents of the history of our planet. 

 Thus he looks upon life in its entirety, its continuous varia- 

 tion of size, form and mode of existence. He realizes that 

 nothing on this earth remains unaltered. 



This is the point at which our modern conception of the 

 living nature differs thoroughly from older views on this sub- 

 ject. Formerly it was questioned whether living organisms 

 are subject to any changes of form at all. As we know, 

 children resemble their parents and the human race has 

 apparently changed but slightly within the entire period of 

 its recorded history. Historic studies therefore readily con- 

 vey the impression that the world of today has existed from 

 all eternity with only slight alterations. 



But the period of recorded human history is only one 

 diminutive fraction of the total existence of the earth. 

 Even within such a limited period we find many exceptions 

 to the rule that the offspring resembles the parents. This 

 rule holds only if the conditions under which the offspring 

 exists remain unchanged; and even then spontaneous varia- 

 tions may sometimes appear. 



We observe baffling variations of the form of animals in 

 consecutive generations when we perform breeding experi- 

 ments where many conditions are varied and where ab- 

 normal, spontaneously appearing types arc propagated on 

 purpose. Darwin has strikingly demonstrated this fact 

 through his renowned studies on domesticated pigeons, 



