THE BELFAST ADDRESS 195 



one. There are organisms whose vital actions are almost 

 as purely physical as the coalescence of such drops of oil. 

 They come into contact and fuse themselves thus together. 

 From such organisms to others a shade higher, from these 

 to others a shade higher still, and on through an ever- 

 ascending series, Mr. Spencer conducts his argument. 

 There' are two obvious factors to be here taken into ac- 

 count — the creature and the medium in which it lives, or, 

 as it is often expressed, the organism and its environment. 

 Mr. Spencer's fundamental principle is, that between these 

 two factors there is incessant interaction. The organism 

 is played upon by the environment, and is modified to 

 meet the requirements of the environment. Life he de- 

 fines to be *'a continuous adjustment of internal relations 

 to external relations." 



In the lowest organisms we have a kind of tactual 

 sense diSused over the entire body; then, through im- 

 pressions from without and their corresponding adjust- 

 ments, special portions of the surface become more re- 

 sponsive to stimuli than others. The senses are nascent, 

 the basis of all of them being that simple tactual sense 

 which the sage Democritus recognized 2,800 years ago as 

 their common progenitor. The action of light, in the first 

 instance, appears to be a mere disturbance of the chemical 

 processes in the animal organism, similar to that which 

 occurs in the leaves of pk.nts. By degrees the action be- 

 comes localized in a few pigment- cells, more sensitive to 

 light than the surrounding tissue. The eye is incipient 

 At first it is merely capable of revealing differences of 

 light and shade produced by bodies close at hand. Fol- 

 lowed, as the interception of the light commonly is, by^ 

 the contact of the closely adjacent opaque body, sight in 



