BRAIN MECHANISMS AND LEARNING 



consideration to the concept of natural selection, but continued to account 

 for the more complex portions of neural evolution primarily in Lamarc- 

 kian terms: 'Regarding as superimposed, each on the preceding, the 

 structural effects produced generation after generation and species after 

 species, we have formed a general conception of the manner in which the 

 most complex nervous systems have arisen out of the simplest. This 



A'.... 



Fig. 2 

 Diagrams of a ganglion prepared by Spencer (17), sliowing the 

 development of superimposed levels of neural co-ordination^ 



general principle can be alleged only on the assumption that changes 

 wrought in nervous structures by nervous functions are inheritable. 

 Throughout the earlier stages of nervous evolution, a leading and perhaps 

 most active cause has been the survival of individuals in which indirect 

 influences have produced favourable variations of nervous structure but, 

 throughout its later stages, the most active cause has been the direct 



