90 THE DATA OF BIOLOGY. 



undergo changes so comparatively numerous as to render the 

 successiveness of their changes a marked characteristic. And 

 it will follow d priori, as we found it to do a posteriori, that 

 the organisms exhibiting Evolution in the highest degree, 

 exhibit the longest or the most rapid succession of changes, 

 or both. Again, it was shown that vital change is 



distinguished from non-vital change by being made up of 

 many simultaneous changes ; and also that creatures possess- 

 ing high vitality are marked off from those possessing low 

 vitality, by the far greater number of their simultaneous 

 changes. Here too there is entire congruity. In First 

 Principles, 116, we reached the conclusion, that a force 

 falling on any aggregate is divided into several forces ; that 

 when the aggregate consists of parts that are unlike, each 

 part becomes a centre of unlike differentiations of the inci- 

 dent force ; and that thus the multiplicity of such differen- 

 tiations must increase with the multiplicity of the unlike 

 parts. It follows necessarily, therefore, that organic aggre- 

 gates, which as a class are distinguished from inorganic 

 aggregates by the greater number of their unlike parts, must 

 be also distinguished from them by the greater number of 

 simultaneous changes they display ; and further that the 

 higher organic aggregates, having more numerous unlike 

 parts than the lower, must undergo more numerous simul- 

 taneous changes. "We next found that the changes 

 occurring in living bodies, are contrasted with those occurring 

 in other bodies, as being much more heterogeneous ; and that 

 the changes occurring in the superior living bodies, are 

 similarly contrasted with those occurring in inferior ones. 

 Well, heterogeneity of function is the correlate of hetero- 

 geneity of structure ; and heterogeneity of structure is the 

 leading distinction between organic and inorganic aggre- 

 gates, as well as between the more highly organized and the 

 more lowly organized. By reaction, an incident force must 

 be rendered multiform in proportion to the multiformity of 

 the aggregate on which it falls ; and hence those most mul- 



