Summary of Conclusions Reached 503 



CHAPTER XVIII. 



Evolution and Distribution of Fishes. 

 Synoptic Review of Previous Chapters.' 



On this and succeeding pages the author presents, in 

 synoptic manner, the main conclusions reached by him in the 

 preceding chapters. These are not necessarily in the exact 

 sequence given in the general text, but are so arranged as to 

 give a fairly condensed, concrete, and continuous idea of 

 the evolution of fishes. 



Chapter i. 



Energy, not matter, is the fundamental factor in organic 

 as in inorganic evolution. 



In the upbuilding and evolution of organic molecules, 

 colloid constituents are essential. 



In the evolution of animals up to the stage of fishes, 

 three progressive condensations of higher or organic energy 

 are necessary, (a) the biotic; (b) the cognitic; (c) the 

 cogitic. 



Such energies when in action start: (i) irritability, 



(2) nutrition, (3) respiration, (4) growth, (5) reproduc- 

 tion, as intrinsic properties or activities of the organism. 



Organic evolution proceeds through joint action and 

 reaction of an organism to environal stimuli. Such evolu- 

 tion is due to the cooperative activity of Pentamorphogeny, 

 or the five factors of (i) heredity; (2) environment; 



(3) proenvironment; (4) selection; (5) reproduction. 

 The ecological factors that act as stimuli are : thermic, 



lumic, chemic, electric, geotropic, (or geotactic), hydro- 

 tactic, and organismal stimuli. 



A detailed study of the factors of Pentamorphogeny is 

 then given. 



Chapter 2. Geologic conditions in relation to the evolu- 

 tion of fishes. 



During primitive evolution of metanemertean, proto- 

 chordate, and chordate organisms, the earth's crust long 



