358 MECHANICAL EVOLUTION. 



pendence of their enyironment of whicli tbey are capable. The 

 first important acquisition leading to this end was aerial respira- 

 tion ; the second, rapid nutrition by hot blood. And as essential 

 to tlie production and preservation of these, improvements in 

 organs of movement have been superadded to every successive 

 type of life. 



Consciousness remains as the unresolvable factor in the process ; 

 as at once the measure of, and respondent to a large class of phe- 

 nomena. 



