THE ENVIRONMENT 49 



as final, there is none at all for the belief 

 that anything essentially inexplicable either 

 physico-chemically or genetically will be dis- 

 covered in their organization. 



Putting aside all contentious matters, it is 

 abundantly clear that nebulae, however they 

 may vary among themselves, are made up of 

 vast extents of gaseous material and dust 

 which are exceedingly rare and at very low 

 temperature, and that they may contain all 

 kinds of foci of condensation, from stars to 

 meteorites, in great variety of forms and 

 conditions. 



On the whole the common-sense judgment 

 that the solar system may be taken as a fair 

 sample of the universe, and that its probable 

 evolution is in the main typical of cosmic 

 evolution in general seems to be well founded. 

 Any other hypothesis does violence to a host 

 of facts, and to the larger generalizations of 

 modern science. 



II 



POSSIBLE ENVIRONMENTS 



If now we seek to make the best of existing 

 astronomical knowledge, as hastily sketched, 

 in the study of our biological problem, cer- 

 tain considerations at once present themselves. 



E 





