THE INTEGRATION OF THE ORGANIC WORLD. 397 



For here it remains to point out that along with the in- 

 creasing multiplication of types of organisms covering the 

 Earth's surface, there has been ever going on an increasing 

 mutual dependence of them — an increasing integration of 

 the entire aggregate of living things. 



Many facts which are obvious and many which are quite 

 familiar will be named as evidence. But I must be excused 

 for reminding the reader of things that he knows and things 

 that he may easily observe, since, unless the evidence, trite 

 as it may be, is gathered together and properly marshalled, 

 the generalization enunciated will not be thought valid. 



§ 314&. Respecting the physiological characters of the 

 earliest forms there is an assumption from which no escape 

 seems possible — the assumption that they united animal and 

 vegetal characters. Even among existing microscopic types 

 of the lowest classes, there is such community of plant- 

 traits and animal-traits that doubts respecting their proper 

 places in one or the other kingdom are continually raised 

 — doubts, too, whether, if regarded as vegetal, they are to be 

 grouped as algoid or fungoid. 



Here, however, without entering on moot questions, we 

 may draw the a priori conclusion that these earliest living 

 things were double-natured, in so far that they must have 

 had the ability to assimilate from the inorganic world all the 

 materials of which protoplasm consists — must therefore, 

 along with the power of appropriating carbon from its gase- 

 ous compound, also have had the power of appropriating ni- 

 trogen, either from one of its combined oxides or directly from 

 the air with which water is more or less charged. For before 

 organic substances existed there could have been none but 

 inorganic sources from which nitrogen could be obtained. 



This conclusion concerns us only because it implies 

 homogeneity of nature in these primordial forms of life. 

 There could not at first have existed among these minutest 

 of Protozoa even such vague distinctions as are now presented 



