278 THE ORIGIN AND EVOLUTION OF LIFE 



or alternating directions taken by the organism in seeking its 

 life environment or physical environment. 



It is true, we have found (p. 264) among the descendants 

 of similar, though remote, ancestors something determinate or 

 definite — a similarity which reminds us of the potential of the 

 physicist — as to the origin of certain characters rather than 

 others in the heredity-chromatin. It is as if certain latent 

 power or potency of character-origin in the chromatin were 

 there waiting to be called forth. It is partly due to this, 

 as well as to inheritance of a similar ancestral form, that the 

 mammals, as studied by the comparative anatomist, are so 

 much alike, despite their superficial differences as seen by the 

 student of adaptation. This definite or determinate origin 

 of certain new characters appears to be partly a matter of 

 hereditary predisposition. That is, animals from a common 

 stock independently give rise at different times to similar new 

 characters, as seen, for example, in the origin of similar horn 

 defenses and similar bony and dental structures. 



The conclusive evidence against an elan vital or internal 

 perfecting tendency, however, is that these characters do 

 not spring up autonomously at any time; they may lie dor- 

 mant or remain rudimentary for great periods of time, and 

 here we find a correspondence which may be only an analogy 

 with the principle of latent energy in physics. They require 

 something to call them forth, to make them active, so to 

 speak. 



It is in this function of arousing such character predis- 

 positions that the chemical messenger phenomena of inter- 

 action in the organism present some analogy to latent energy, 

 although future experiment may prove that this does not con- 

 stitute a real cause or likeness. If the transformation of energy 

 is accelerated in certain organs or parts of existing organs by the 



