1014 The American Naturalist. [November, 
The latter throws only its own indurated cilia; the beaver uses 
the earth for burrowing, the water for covering, and the timber 
for building both the dam and its house. The more complex 
the performance the more likely is the animal to employ also the 
deductive act. Thus inthe case of the building of nests by birds 
and trap-door spiders, when customary materials are wanting, 
new ones are adopted; that is, a known rule as applied to new 
cases. 
The manner of the evolution of the concept has been as fol- 
lows: The sensible qualities of objects are first learned, and 
stored in the memory. The qualities must be distinctly localized 
in the nervous centers, otherwise confusion of memory would 
result. Thus if a red bird is perceived to sing on a tree four 
distinct perceptions are experienced. First, a bird’s form; sec- 
ond, a red color; third, the song of a bird; fourth, a particular 
tree on which the bird was perched. It is not probable that that 
part of the nervous center which perceives form is identical with 
that which perceives color, nor either with that which perceives 
sound. The constituent parts of the center have become special- 
ized into different regions, each capable of apprehending a differ- 
ent quality. Each locality is blind or deaf, as the case may be, 
to that stimulus which affects the other, although all may be 
alike reached by the vibrations, or whatever the form of stimulus 
may be, which is derived from the common source. And each is 
so joined by connecting nervous threads with all of the other 
localities, that the general idea of the entire object is not lost. 
Thus we may believe that there is a localization of the sense of 
form, where forms are recorded, and may be compared and their 
identity or difference be consciously known. In simple minds 
identity would be often perceived, and slight differences be disre- 
garded. Hence the simple conceptions of the animal mind. In 
more advanced minds, with greater specialization and organiza- 
tion of structure, minuter differences, as well as wider resemblances 
would be recorded, and would enter into consciousness. The com- 
bination of percepts form the lowest grade of concepts, Still 
higher development would render possible wider combinations 
through the development of nervous connections between more 
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