966 The American Naturalist. [December, 
Under this conception, we may look upon the rise and de- 
velopment of sense organs generally to mean the slow differ- 
entiation of protoplasm to the exclusive use of certain specific 
forms of stimulation. Thus we may interpret the appearance 
of eyes to mean the production of an apparatus peculiarly 
adapted for light waves to the exclusion of all other forms of 
stimuli. Through the appropriation of the entire fixed sur- 
face of our bodies to the particular sense organs which devel- 
oped in our ancestry, we see how, under this proposition, our 
few kinds of sense should have been preserved to us; and how 
the infinite number of others with which it endows primitive 
protoplasm, should be lost to’ us through the required forms of 
stimulation being shut out. 
The alternative of this fundamental formula is that we may 
conceive, quite oppositely, that protoplasm was capable at first 
of only one form of sensory response ; and of but one mode of 
neuro-sensory activity correspondent therewith. What this 
form of sense was we need not consider, at „present, further 
than to suspect that it may have been far different from any- 
thing we experience. 
Under this proposition we should attribute the rise of vari- 
ous new senses: to the development of new kinds of proto- 
plasm, capable of correspondently new forms of sensation. 
Thus the advent of sight and of sight organs, here, would 
mean the development of a new basis of physical activities, 
peculiarly susceptible to light stimulation, and the psychic 
counterpart of which would be a new kind of sense. 
These, then, are our opposing hypotheses. According to 
one, Life began with many fleeting, transitory senses, and we have 
become shut in to a few permanent and highly developed ones. Ac- 
cording to the other, Life began with one simple sense, and has 
opened outward with the development of our various and compli- 
cated senses. 
It will now be proper to bring forward the implications of 
these great rival theories in a way to justify the lofty pros- 
pectus which we have announced for them. 
First we should note, as cee has been intimated, Be - = 
both propositions, alike fi assume different 
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