42 



SUPER-ORGANIC EVOLUTION 



To understand the genesis of the neuronas, one 

 must go back to inferior animals like the gastrula 

 (vide fig. 1). The cells which constitute its 

 external covering, called ectoderm, are the first 

 organs of the nervous system. From its direct 



FIG. 2. 



A, mio-epithelial cells of the actiniaries (coelenterade) ; a, peripheric end with 

 a cilium ; &, middle part, which contains the nucleus ; c, the deep part of 

 the cell differentiated by a contractible fibre. B, muscular ectodermic 

 fibres. (According to 0. and R. Hertwig. ) 



relation with the exterior they are the first registers 

 of these special rhythms, which are those which 

 give to the nervous element its significance. In 

 virtue of these affinities with the external agents 

 cells are created, like the red corpuscule of the 



