PSYCHIC ADAPTATION 95 



That intelligence is an adaptation of natural 

 laws is a fact admitted but little known. Such 

 importance has the descent of intelligence as a 

 result of psychic evolution, that Haeckel even 

 noticed that the application of this knowledge to 

 psychology would result in the transformation of 

 modern science. 



In order to thoroughly understand H. Spencer's 

 inductions on this head, we must study the actual 

 facts, which such an authority on the subject as 

 the illustrious neurologist Eamon y Cajal made 

 known to the International Medical Congress in 

 Rome : 



" In the animal kingdom, the nerve-cell represents 

 a series of evolutive terms corresponding to the 

 phases which the neuroblastoderm of His passes 

 through in the ontology of the mammiferae. . . . 

 Here, as in other organic textures, ontogeny is a 

 resume, with slight variations, of phylogeny. 



" The following are the evolutive ontogenic phases, 

 with the phylogenic gradation to which they corre- 

 spond (see fig. 12) : 



" First Phase : Neuroblastoderm of His. Is a pear- 

 shaped cell, of smooth surface, provided with a 

 single expansion, the cylindric axis, which terminates 

 within or without the nerve-centres, due to a free 

 ramification more or less extensive. This prim- 

 ordial form is represented, as is proved by the 



