The Origin of Life 21 



In 1883 the small island of Klrakatau was destroyed 

 by the most violent volcanic eruption on record. A 

 visit to the islands two months after the eruption 

 showed that "the three islands were covered with 

 pumice and layers of ash reaching on an average a 

 thickness of thirty metres and frequently sixty metres." ^ 

 Of course all life on the islands was extinct. When 

 Treub in 1886 first visited the island, he found that 

 blue-green algse were the first colonists on the pumice 

 and on the exposed blocks of rock in the ravines on 

 the mountain slopes. Investigations made during 

 subsequent expeditions demonstrated the association 

 of diatoms and bacteria. All of these were probably 

 carried by the wind. The algae referred to were accord- 

 ing to Euler of the nostoc type. Nostoc does not re- 

 quire sugar, since it can produce that compound from 

 the CO 2 of the air by the activity of its chlorophyll. 

 This organism possesses also the power of assimilating 

 the free nitrogen of the air. From these observations 

 and because the NostocacecB generally appear as the 

 first settlers on sand the conclusion has been drawn 

 that they or the group of Schizophycece to which they 

 belong formed the first settlers of our planet.^ This 

 conclusion is not quite safe since in the settlement of 

 Krakatau as well as in the first colonizing of sand 



' Ernst, A., The New Flora of the Volcanic Island of Krakatau^ 

 Cambridge, 1908. 



^ Euler, H., Pflanzenchemie, 1909, ii. and iii., 140. 



