8 The American Naturalist. [January, 
(Oi w). Under the Weismannian principle, we may conceive 
the same general plan of developnent to have proceeded, here, 
as formerly under this principle (Od w) with reference to the 
-birth of each new sense, but with a more complicated pro- 
gramme with reference to the couplings of inner sensations with 
different outer forces, at different periods. Relative to this last 
we may observe that, since the permanency of intermediate 
articulations must depend on the permanency of the organs 
that perform them, therefore it is not likely, that the precise 
couplings now obtaining in us were constant or, perhaps, 
occurred at all before these organs developed. Under these 
conditions it would be even more difficult to follow the his- 
tory of our sense-origins, than under the method of our last 
above paragraph. The method of this present paragraph, 
however, may be exampled, if it should prove true that the 
phenomena of color-blindness are due to the failure of birth 
in certain people and species, of neural variations sufficiently 
differentiated to be responsive to the solar waves in the 
fuller way exhibited in our normal color spectrum. Some- 
thing like this is demanded to explain the origin of color sen- 
sations under Prof. Wundt’s theory of vision. 
(Oil). Under the Lamarckian principle, as under the Weis- — 
mannian, the intermediate processes would but complicate — 
the general plan of evolution outlined under direct articula- _ 
tion (O41). And again the Morgan explanation of otic mor- 
phology may serve as an example, except that now we should ; 
no longer conceive vibration of the otic cilia to have direct — 
determination of the auditory impulses; but should be obliged 
to consider certain as yet undetermined mediatory processes, — 
including, perhaps, unknown chemical activities in the otic — 
cells. 
several senses have risen at successive periods, and that for — 
_ each of them the peculiar fitness of its underlying neural corre- 
spondence has been the ultimately determining factor of its — 
birth and selective perpetuation from among other possible 
senses, and also of its connection with its present stimulus. 
SPS TS OE ip, OM rn Pane Chee ae oe 
See oN ed eee, MRE eae as “3 Ae fee 
are yer 
The last above four paragraphs exhaust, if I mistake not, the 4 
evolutionary possibilities under the postulate that life began — 
with one sense; the central idea in each case being that our — 
