Evidence.

It will be asked what evidence there is for the view here put forward that such is the order and method of the construc­tion of the central nervous system. There are two classes of evidence. The first direct, and the second indirect and resting on inference. The well-known leads to the less-known and inferred. Direct evidence of the founda­tion of new reflex-arcs and their organiza­tion is of course small. The conditions, such as the duration of human life, preclude any extensive formation under experiment of new reflex-arcs, but enough is known to enable one to follow the backward way with some confidence. As to the inheritance of these, the evidence rests on opinion and tremendous probability, but as the only problem with which I am concerned here is that of initiative I think it better to leave the matter of transmission to a dispassionate considera­tion of the probability of its occurrence.