218 LECTURES ON BIOLOGY 



In spite of their potential immortality numberless individuals con- 

 tinually sank to the bottom, their bodies decaying, but their tiny 

 shells accumulating. Generation followed generation, and higher 

 and higher rose these mountains of corpses until they almost 

 reached the surface. Now follows a period of enormous revolu- 

 tions of the earth's interior or contractions of the rigid crust : the 

 sea floor rises and from the floods ascend the mountains of dead 

 Foraminifera, an enormous continent of chalk. But what Nature 

 builds to-day she destroys to-morrow, for nothing in this world 

 is eternally constant except alone change. 



Keines verbleibt in der gleichen Gestalt, denn Veranderung liebend, 

 Schafft die Natur stets neu aus anderen andere Formen, 

 Doch in der Weite der Welt geht iiichts das glaubt mir verloren. 

 Wechsel und Tausch ist nur in der Form, Entstehen und Werden, 

 Heisst nur anders als sonst anfangen zu sein, und Vergehen, 

 Nicht mehr sein wie zuvor. Goethe. 



Kain and wind beat incessantly against these rocky masses, 

 and cut deep valleys into the land ; the sea follows, completing 

 the work of destruction, but what it tears away in one place it 

 deposits in another. Such alternations of destruction and con- 

 struction created the island of Riigen in its rugged shape as 

 we know it to-day. But still the waves thunder against the 

 chalk cliffs, and rain and storm continually carry away to the 

 sea earth and fragments of stone. Many thousands of years 

 may yet have to pass, but the day will come when Kiigen will 

 be no more, just as there was once a time when it was not yet. 

 But the ' becoming ' is eternal. Billions of Foraminifera still 

 people the ocean the descendants of those whose shells built 

 the island of Riigen and they will make new lands and new 

 islands arise. But it takes longer than the short life of man to 

 observe Nature in its giant task. The enormous numbers of 

 lives which must be born and die before one single chalk-rock 

 can be built will be understood when we hear that one gramme 

 of chalk contains more than fifty thousand shells of Foraminifera. 



Foraminifera played an important role in other parts of the 

 earth's history. In the Carboniferous Formations we know in 

 many districts extended strata which consist almost exclusively 

 of shells of Fusulina and Schioagerina. In the Tertiary Period 

 we encounter, especially in Southern Europe, in the Carpathians 



