102 THE DATA OF BIOLOGY. 



have any simultaneous and successive changes answering to 

 them in the organism. A plant s vital processes display 

 adjustment solely to the continuous co-existence of certain 

 elements and forces surrounding its roots and leaves; and 

 vary only with the variations produced in these elements and 

 forces by the Sun are unaffected by the countless mechanical 

 movements and contacts occurring around; save when acci 

 dentally arrested by these. The life of a worm is made up of 

 actions referring to little else than the tangible properties of 

 adjacent things. All those visible and audible changes 

 which happen near it, and are connected with other changes 

 that may presently destroy it, pass unrecognized produce in 

 it no adapted changes : its only adjustment of internal rela 

 tions to external relations of this order, being seen when it 

 escapes to the surface on feeling the vibrations produced by 

 an approaching mole. Adjusted as are the proceedings of a 

 bird to a far greater number of co-existences and sequences 

 in the environment, cognizable by sight, hearing, scent, and 

 their combinations : and numerous as are the dangers it shuns 

 and the needs it fulfils in virtue of this extensive correspond 

 ence; it exhibits no such actions as those by which a human 

 being counterbalances variations in temperature and supply 

 of food, consequent on the seasons. And when we see the 

 plant eaten, the worm trodden on, the bird dead from starva 

 tion; we see alike that the death is an arrest of such corre 

 spondence as existed, that it occurred when there was some 

 change in the environment to which the organism made no 

 answering change, and that thus, both in shortness and sim 

 plicity, the life was incomplete in proportion as the corre 

 spondence was incomplete. Progress towards more prolonged 

 and higher life, evidently implies ability to respond to less 

 general co-existences and sequences. Each step upwards must 

 consist in adding to the previously-adjusted relations of 

 actions or structures which the organism exhibits, some 

 further relation parallel to a further relation in the environ 

 ment. And the greater correspondence thus established, must, 



