50 THE FITNESS OF THE ENVIRONMENT 



Obviously it is not everywhere in such a uni- 

 verse that life can exist. The visible stars, 

 like the sun, certainly cannot support life. 

 Throughout such bodies durable and complex 

 arrangements of matter are impossible, for if 

 formed, they must be at once dissipated by 

 catastrophes far greater than any which can 

 occur upon the earth's crust. The enormous 

 intensity of heat, even in the most superficial 

 parts of suns, must effectually preclude any 

 state of matter but the gaseous, and thus 

 prevent the existence there of anything of 

 the nature of a mechanism. Such bodies, 

 apart only from continuous variation from 

 center to periphery, in the proportions of the 

 elements, in density, and in the nature of the 

 chemical unions between the elements, must be 

 essentially homogeneous. They can scarcely 

 possess relatively as much structure as the 

 earth's atmosphere. In truth the sun itself 

 seems to be the one and only durable solar 

 mechanism. 



Not less evident is the impossibility of active 

 life in interstellar space or in nebulae. Dor- 

 mant life (panspermia) may indeed be possible 

 universally, except only in the neighborhood 

 of suns. But if life is to be fed, if there is to 

 be active metabolism, including exchange of 

 matter with the environment, something more 



