490 The Polar Organization of Animals. [May, 4 
double-sexed organism. In the higher animals a superior differ- : 
entiation arises, in the division of sexual polarity between distinct — 
individuals, yet its minor phase of the doubly-sexual organization — 
of each individual, is still retained. ; 
The other polarity of protoplasm mentioned is equally declared 
in the highest animals. As the former remains a lateral, this be- 
comes a longitudinal polarity, as we shall seek to show. Origin- 
ally it is a polar or functional difference of the external and inter — 
nal layers. This distinction persists in the highest animals, but — 
each of the two functions gains its distinct pole. 4 
The pole of the sensory function is not difficult to discover. It 
becomes gradually declared as we ascend beyond the lower air — 
mals, and displays itself in all the higher animal forms as the | 
brain. This organ is the center of the motor and sensory nerve 
fibers which collects, retains and again disseminates the impres- : 
sions arising from external contact. Such an organ is perhaps | 
not needed by lower organisms. Their defective sensory and : 
motor organs render them but feebly sensitive to impression, and 7 
they can easily respond to every contact of sufficient vigor tè 1 
“overcome the sluggishness of their organs of sensation. But the l 
whole course of development is towards a greater and more diver” 
sified sensitiveness of the animal form. The highest animals a 
respond to impressions of excessive delicacy. Almost every = A 
influence of the outer world is capable of affecting them, whi 5 
their complex muscular organization permits of a great vanci 
responsive motions. ; -l 
Yet evidently a movement in response to every impression; > 
after such extreme sensitiveness is attained, would be p 
injurious. The vigor of the organism would be exhausted. i 
with the increase of sensitiveness there became necessary the: is 
lution of some discriminative organ, some center of eee 
which the motor energies received could be retained, a : 
ed, only 
be- 
which the movements of the muscles could be controll pie 
such impulses as were likely to be beneficial to the pase his : 
ing permitted to pass onward. With the modus operandi | a 
process we are not here concerned. It suffices eee : 
retention of and descrimination between nerve imprest : 
necessary ere any high development could be gained, oe 4 
brain was evolved as the organ of this retention. The pase all 
therefore, the true pole of the sensory function. Thithers™ 
