Introduction 13 



Sudden or slow denudation changes, alterations in the 

 relation and elevation or depression of land alongside rivers 

 and seas, the setting free into waters, of beneficial or of 

 deleterious food compounds, the presence or absence of par- 

 ticles so large or so fine as to interfere with respiratory 

 change, the existence of barriers that might prevent or of 

 passages that might promote, distribution of individuals 

 or species, all need consideration. 



But those much more complex exhibitions of organic 

 energy that we group as bacterial and fungoid diseases, 

 or as animal parasites, may likewise operate as environal 

 factors of prime importance. 



In the separate or joint action of the above stimuli or 

 energized factors, as being environal exhibitions of energy, 

 each organism is affected to varying extent and responds 

 accordingly. So by slow degree the five above named co- 

 operating agencies of Pentamorphogeny, viz. Heredity, En- 

 vironment, Proenvironment, Selection, and Reproduction 

 have become impressed on each organism as a result of the 

 conjoint actions of all external agents, and the conjoint 

 reactions that each organism has shown to such actions. 

 The sum total of these actions and reactions causes evolu- 

 tion, equilibrium or devolution in each organism, either 

 temporarily or permanently, up to the period of death. 

 Each of these factors can now be briefly reviewed. 



I. HEREDITY. 



Since, in the gradual evolution of the earth, the sim- 

 pler inorganic compounds were formed step by step as 

 cooling and crystallization proceeded, so in the varied and 

 long continued actions and reactions between organisms 

 and the sum total of their environment, definite structures 

 have been built up that show definite structural details so 

 long as the environment remains fairly constant. For it is 

 undoubtedly true, in the past history of the world, that 

 there was a time when such inorganic bodies as carbonate 

 of lime, sulphate of soda, or potassium phosphate did not 

 and could not exist, owing to unsuitable environal condi- 

 tions. But given the needed environal states, the simpler 

 constituents of these bodies united into stable union and 



