10 



LIFE S BEGINNING ON THE EARTH 



We can hardly expect to find traces of their past existence in 

 the crust of the earth. In the laboratory, however, we can 

 find some developments of non-living matter which show a 

 faint resemblance to certain features of life. To the de- 

 scription of studies of this type we devote this book. 



Shark 



Alligator 



Oppossum Lemur 



Fig. 3. Development of the Head, Fish to Man 

 (series continued on next page) 



In order to understand the origin of life, it is not sufficient 

 to describe in all details the make-up of the countless types 

 of living cells, or the functioning of organs of living animals. 

 We must seek addil ional avenues of approach by finding life- 

 like features in non-living mat fcer. This line of investigation 

 is still much neglected a1 present on account of the prevailing 

 impression that a gap exists between living and non-living- 

 nature. 



