1896.] The Biologie Origin of Mental Variety : 975 
period at which a spontaneous variation made a new kind of 
“sense energy” possible. Thus, the present connection of 
cerebral sight with the optic nerve and with the eyes, and with 
the light that falls on them, might well, for all we know to the 
contrary, be entirely due to the chance appearance of a new 
form of “energy ” or molecular possibility in the cortex just 
at a time when the development of optic end-organs made a 
connection with the new cerebral development available, and 
the exigences of the outer environment made the new linkage 
of processes of service. Such a connection of inner sense to 
outer stimulus would be as accidental as anything can be, yet 
it might be adequate for explaining the facts of our problem 
were no influences to be considered that might disturb the perma- 
nency of such connections. And this brings us finally to the 
influences which most surely would have disturbed the perma- 
nency which actually has been maintained, had this theory 
that the sensory nerve currents are alike been really in force. 
These disturbing influences become apparent when we con- 
sider the uniformity of the functions that would be left to- 
central nervous processes under the conditions of this theory. 
No one has ever contended that the outgoing currents of the 
motor nerves are of diverse kinds. If, therefore, the incoming 
currents. were also all alike, there would then be left to the 
central processes the entirely homogeneous switch-board func- 
tion of connecting like currents with like currents. And, 
under such conditions, and cut off from all diversity of external 
influences, it seems scarcely possible that some one form of 
molecular activity or “sense energy” out of the many that 
variation may have given birth ito or protoplasm been origin- 
ally capable of, would not prove most suitable to this one 
purpose, and as a consequence become perpetuated to the ex- 
clusion of all other less suitable kinds of neural sense-forms. 
Or, put again more simply, since moleculur forms are sure to have 
been evolutionary determinants, therefore, if all the nerve currents were 
alike it seems certain that the cortical processes must also have become 
alike. And since this manifestly is not the case, therefore we 
must abandon Prof. James’ theory. 
(To be Continued.) 
