1897] The Biologic Origin of Mental Variety : 7 
ing upon our own sensory equipment as the outcome of this 
process, we must conceive each present coupling of sense and 
appropriate stimulus to be one that has existed unaltered since 
the first appearance of that sense. Asan example of this we 
must conceive, that although many primitive creatures display 
actinic susceptability, yet they experience thereby no such color 
sensations as we do; that these last were born in to the line of 
our ancestry at an unknown period, (not necessarily coincident 
with the appearance of eyes); and that the rise of serviceable 
end-apparatus has gradually specialized the neural basis of 
these sensations to a coupling with certain ranges of ether- 
vibration called light.’ 
(O41). Under the Lamarckian principle we may conceive 
that the diversity of environmental forces played on the devel- 
oping organism, from without, each in a way tending to mod- 
ify the nervous mechanism to its own peculiarities and needs, 
and to mould the total organism: in accord with its net func- 
tional efficiency within, again, our full five evolutionary 
spheres. In this case it would be extremely difficult to deter- 
mine whether the sort of.sense that now responds to any given 
stimulus, let us say light, is at all like that which responds to 
the same stimulus in primitive creatures. An actual example 
of this mode of development may possibly be found in the his- 
tory of our ears ; that is, if as Prof. Lloyd Morgan has suggested, 
gross vibrations, such as rolling the body, were the appropriate 
stimuli for the cilia of the otic organs at a primitive stage of 
development, a crude sense of equilibrium being the psychic 
result; and if our present hearing has come about by perfect- 
ing adjustment of these organs, continuously, to finer and finer 
vibrations, while a correspondent change took place in re- 
spondent sensations. 
Starting again with the same postulate of one primary sense, 
we must next couple it with the doctrine of intermediate arti- 
culative processes in the end-apparatus. 
1 Since there is evidence that amorphous creatures react to various stimuli, if 
we suppose but one primitive sense, we must conceive that it responds, alike, to 
several forces. Also similarly for each newly appearing sense. Under these 
conditions, the narrowing of each of our senses to its present stimulus, is to be 
explained by morphologic specialization. 
