44 CARNEGIE INSTITUTION OF WASHINCxTON. 



Leaving these chances, we may now turn to the daily work. It 

 is that work which cahiily and steadily increases our knowledge and 

 which is the most assured way to success, even if the advance is less 

 striking and seemingly slower than in the alluring experiments 

 alluded to. 



The process of the evolution of animals and plants has to be at- 

 tacked by direct experiment. This evolution, however, has a long 

 history, covering many millions of years. Its historical part, of 

 course, is not accessible to experimental work. From its innermost 

 nature it must be studied according to historical and comparative 

 methods. In laboratory work we may simply pass it by. 



After eliminating this great mass of detail concerning the pedigree 

 of the animal and vegetable kingdom, two points remain, which pre- 

 sent themselves for experimental study. These are the beginning 

 and the end. Obviously the real end is not yet reached, evolution 

 going even now steadily on. In the same waj^ we may assume that 

 the beginning is not yet finished. The laws that ruled the material 

 world some twent}' or thirty millions of years ago must have been 

 the same that are still ruling it in our days. Circumstances may 

 have changed, but it is not very probable that those which permitted 

 life at the beginning and those which have made it possible during 

 the long geological ages should have been widely different. Quite 

 on the contrary, it seems only natural to assume that new life may 

 nowadays originate as well as in former times. It is only a question 

 of where we are to look for it. 



On this very difficult point I like to be guided by the genial con- 

 ceptions of Brooks. In his "Foundations of Zoology " he depicts 

 the primeval seas and their living population. All life must have 

 been limited at those early periods to the high sea ; all organisms 

 were floating amid the waves, going onl}- to a depth of some few 

 meters. Here the main lines of the animal and vegetable pedigree 

 must have been produced, starting the great divisions of both king- 

 doms. The only exceptions are offered by the flowering plants and 

 the vertebrate animals, which seem to have originated on the shores 

 or perhaps on the land itself. As long as all life was in this floating 

 condition, evolution proceeded rapidly and broadened out. Then 

 came a period when, as Brooks says, the organic world made the 

 discovery of the possibility of living on the bottom of the sea, feed- 

 ing on the sinking remains of the floating world. This great change 

 was the starting point for numerous adaptations and for the evolu- 

 tion of a richness of forms and structures, but without the previous 

 progress in the production of many really new divisions. 



