Adaptability of Living Matter 55 



the play of an ever-varying environment. It 

 could only have been brought about by some 

 definite and persistent force underlying or 

 working with that implied under the term of 

 natural selection. (See Appendix.) As regards 

 the development of the structures forming the 

 organ of vision, it appears to us we have in that 

 mode of energy we call light a force capable 

 of moulding, on general lines, living substance 

 so as to adapt it to the needs of the various 

 ascending orders of beings. It is evident that 

 waves of sunlight must have acted constantly on 

 organic matter from the time this substance first 

 came into being. It is, therefore, conceivable 

 that light might, in the course of time, have 

 moulded the molecules of primitive forms of 

 organic matter into structures which gradually 

 became adapted to its own incidence, as well as 

 to that of the environment. The similarity of 

 the structure constituting the visual organs of 

 different classes of animals can thus be ac- 

 counted for, their living substance having re- 

 sponded in like manner to a direct and never- 

 failing similar form of energy. The more and 

 more complex structures forming the eyes of 



