26 DEVELOPMENT AND HEREDITY. 



science cannot be neglected in biological research. 

 The law of the conservation of energy which is fun- 

 damental in the science of physics, when analysed in 

 detail in its application to the phenomena of living 

 matter, has a most extensive import and profound 

 significance. It means that whatever forces of growth 

 and development may be displayed by living organ- 

 isms, these forces must have their sufficient physical 

 causes. We can only regard them as transforma- 

 tions of the general sum of energy. That any con- 

 ceivable part of the energy now displayed by living 

 matter in its various forms should have originally 

 resided in the ancestral forms of life, is unimagin- 

 able. We have no ground to suppose that proto- 

 plasm in its lowest form, and at its first appearance 

 on the earth, possessed any powers except those 

 which are found to be its universal properties to-day, 

 — just as the amoeba now does not contain in itself 

 the forces necessary to produce a mammal. So long 

 as nourishment was supplied, and the proper chem- 

 ical changes kept up in this original living matter, 

 so long would life continue ; but all changes in shape, 

 and all changes in the method of activity, must have 

 been the result of additional force from without. 

 Therefore if we are to account for the various forces 

 displayed by living organisms, either in their indi- 

 vidual activity and growth or in their racial devel- 



