THE BELFAST ADDRESS. 183 



organisms whose vital actions are almost as purely phy- 

 sical 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 argu- 

 ment. There are two obvious factors to be here taken 

 into account 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 in- 

 teraction. The' organism is played upon by the en- 

 vironment, and is modified to meet the requirements 

 of the environment. Life he defines to be * a continu- 

 ous adjustment of internal relations to external rela- 

 tions.' 



In the lowest organisms we have a kind of tactual 

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

 pressions from without and their corresponding adjust- 

 ments, special portions of the surface become more 

 responsive to stimuli than others. The senses are 

 nascent, the basis of all of them being that simple tactual 

 sense which the sage Democritius recognised 2,300 

 years ago as their common progenitor. The action 

 of light, in the first instance, appears to be a mere dis- 

 turbance of the chemical processes in the animal or- 

 ganism, similar to that which occurs in the leaves of 

 plants. By degrees the action becomes localised 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. Followed, as 

 the interception of the light commonly is, by the con- 

 tact of the closely adjacent opaque body, sight in this 

 condition becomes a kind of ' anticipatory touch/ The 



