26 SUPER-ORGANIC EVOLUTION 



the crystal whose differentiation makes it sensible to 

 light. As the mechanical conditions of Nature are 

 invariable, the great unity represented by all 

 comparative anatomy and embryology follows ; 

 therefore, ontogeny reproduces phylogeny, and all 

 this organic unity which constitutes the organisa- 

 tion is the echo, the reflection, the material 

 reproduction of the great rhythms of natural forces. 

 Without this invariable unity which is Nature, there 

 would be no explanation of the phenomenon of 

 evolution, there would be no possibility of tracing 

 the sense of sight from that of the most inferior 

 animals up to that of man. And the human brain 

 would have no explanation either, if there did not 

 exist the same elaboration, affiliation, and evolution 

 of the nervous system of all animals, and if the 

 psychical neurona or thinking apparatus of man had 

 not its first representation in the mio-epithelial 

 nervous system of the lower animals. 



Nobody would now venture to deny (because it 

 is a common conception in positive philosophy) that 

 all the senses are specific numerical registers of 

 movements which constitute the sensations, and 

 that the development of these senses, the accumula- 

 tion of all these sensations, is that which gives rise 

 to the development of the brain in such a way that 

 one feels that without the senses there would be no 

 brain. Then, if the senses obey the laws of Nature 



