RETROSPECT AND PROSPECT 279 



arrival of interacting chemical messengers and these parts 

 thereby change their form and proportions, it is not incon- 

 ceivable that chemical messengers may arouse a latent new 

 character by stimulating the transformation of energy at a 

 specific point. 



Then character-velocity must be considered. Although 

 we may find that in the course of evolution in one group of 

 animals a character moves extremely slowly, it lags along, 

 it is retarded, as if partly suffering from inertia, or perhaps, 

 for a while it stops altogether; yet in another group we may 

 find that the very same character is full of life and velocity, 

 it is accelerated like the alert soldier in the regiment. Here 

 again is a point where the energy conception of evolution may 

 throw a gleam of light. Some of the phenomena of interaction 

 in the organism give us the first insight into the possible causes 

 of the slow or rapid movement of character evolution — of its 

 acceleration and retardation. Such individual character move- 

 ments may govern the proportions of certain parts as well 

 as of all parts of the organism. 



Combined, these character velocities and movements create 

 all the extraordinary differences of proportion which dis- 

 tinguish the mammals — for example, the extraordinarily long 

 neck of the giraffe, the short neck of the elephant, the elongated 

 skull of the ant-eater, the abbreviated head of the tree sloth. 

 Wherever such changes of proportion weigh in the struggle 

 for existence they may be hastened or retarded by natural 

 selection. 



We discover that the chief principles of comparative 

 anatomy formulated by Aristotle, Cuvier, Lamarck, Goethe, 

 St. Hilaire, Dohrn, and other philosophic anatomists^ may 

 all be expressed anew in terms treating the organism as a 



' Russell, E. S., 1916. 



