320 THE DOCTRINE OF DESCENT. 



organic combinations existed wliich (p. 556) were under tiie influ- 

 ence of a damp atmosphere, abounding in carbonic acid, and of a 

 higher temperature, light, and stronger electric influences. If these 

 presuppositions are adopted, and the consideration added that if 

 conditions thus favourable to primordial generation once existed, 

 which they must have done — they probably endured during con- 

 siderable geological periods — the inference is in truth inevitable 

 that in lapse of time and with change of circumstances, these 

 organic substances aggregated into innumerable combinations. 

 Among these innumerable modes of arrangement, groupings and 

 combinations, by far the greater portion must remain at the 

 ■grade of inorganic form, because it has not attained the needful 

 chemical composition and physical properties ; a very much small- 

 er portion of the results produced by these combinations of or- 

 ganic materials might perhaps transitorily approach the organic 

 form or even actually assume it, yet without possessing the con- 

 stitution necessary to maintain it permanently ; a third and yet 

 smaller portion might perhaps maintain this form for itself in 

 the exchange of material, about as long as the approximate du- 

 ration of life of one of the most primitive of the present Pro- 

 tists, yet lacked those properties which preserve the species by 

 division and reproduction after the natural extinction of the 

 individual ; a fourth portion might possess the properties requi- 

 site for self-preservation as well as for the preservation of the 

 genus, yet Incked that peculiar tendency to vary (Philosophie'des 

 Unbewussten, p. 591). or at least that tendency to vary in the 

 particular direction which was alone capable of leading to de- 

 velopment into higher forms ; and finally a fifth portion possessed 

 this property in addition to the others. It is the progeny of the 

 fourth and fifth classes of our division which still populates the 

 ocean and the earth.* From which species of Monera pro- 

 ceeded the advanced development of the Infusoria ; whether 

 from one still living or from an extinct species we do not know 



* It is a simpler and more probable explanation that these low 

 organisms continue to exist because there is room for them. They 

 remain in spite of differentiation and in consequence of differentia- 

 tion. 



