GREAT STEPS IN EVOLUTION 69 



series the student will be helped to fill in 

 some of the details of the evolution chart, 

 thus Dr. Scott deals with the pedigree of 

 Plants, Professor Gamble with Animal Life, 

 Dr. Keith and Mr. Marett between them 

 with man; what we propose in this chapter 

 is to indicate in a general way a few of the 

 great steps in OrganigJEvoIutiorL 



THE BEGINNINGS. Until the earth cooled 

 and consolidatedTTwas quite unfit to be a 

 home of life. It follows that at some un- 

 certain, but inconceivably distant date, living 

 creatures appeared on the scene. The ques- 

 tion is : What was the manner of their be- 

 coming upon the previously tenantless earth? 

 Our answer must be that we do not know. 

 But to obviate worse answers we may submit 

 two or three suggestions. 



be that, g^nns n f Ufa game, to mm 



garth embosomed in meteorites. This was 

 the suggestion of Richter, Helmholtz and 

 Lord Kelvin. But it is difficult to conceive 

 of anything like the protoplasm we know 

 surviving transport in a meteorite. 



Some authorities who have found satisfac- 

 tion in the meteorite- vehicle theory have also 

 suggested that life is as old as matter. It 

 must be noted, however, that the life we 

 know is always asjodatejijsith- Mghly ..com- 

 plex substances known as proteids, which 



