All of these operations are, in their beginnings, exceedingly simple; yet, as organisms increase in complexity, these simple beginnings become more complex and more highly developed.
Heretofore, the operations described have been entirely ganglionic (reflex) and utterly without that which we call consciousness. Now, since consciousness, as I understand it, is simply a knowledge of existence, and since this knowledge of existence is only to be had through sensual perceptions, and, since sensual perceptions are excited undoubtedly by coördinated stimuli, then, "there cannot be coördination of many stimuli without some ganglion through which they are all brought into relation. In the process of bringing these into relation, this ganglion must be subject to the influence of each—must undergo many changes. And the quick succession of changes in a ganglion, implying as it does perpetual experiences of differences and likenesses, constitute the raw material of consciousness."[27]
However quick this succession of changes may be, there must be an interval of time between the application of the stimulus and the response to that stimulus, hence, the element of time enters into all psychical operations that are not distinctly reflex. Even in the reflexes there is a time element, but it is distinctly shorter than the time interval that enters into the make-up of a conscious psychical operation. This can easily be demonstrated, as has been done, time and again, by actual experiment.
"With this gradual dawn of consciousness as revealed to subjective analysis, we should expect some facts of physiology, or of objective analysis, to correspond; and this we do find. For in our own organisms we know that reflex actions are not accompanied by consciousness, although the complexity of the nerve-muscular systems concerned in these actions may be very considerable. Clearly, therefore, it is not mere complexity of ganglionic action that determines consciousness. What, then, is the difference between the mode of operation of the cerebral hemispheres and that of the lower ganglia, which may be taken to correspond with the great subjective distinction between the consciousness which may attend the former and the no-consciousness which is invariably characteristic of the latter? I think that the only difference that can be pointed to is a difference of rate of time."[28]
The gradual cultivation of the senses (evolution), during which the special adaptations of their motor reactions are gradually developed, is a necessary prerequisite to the formation and elaboration of conscious volition.[29] In the foregoing pages I have very briefly discussed this cultivation of the senses and the development of their motor reactions. I have likewise outlined the origin of volition from sensual perceptions; it now becomes necessary in this discussion of mind, in the lower animals, to study those organisms in which volition (choice) first makes its appearance in the shape of conscious determination.
Stentor polymorphus is exceedingly interesting on more than one account. Its queer, trumpet-like shape, with its flaring, bell-like, open mouth (if I may use such a term to indicate its entire cephalic extremity), surmounted by rows of vibratile cilia, its pulsating contractile vesicle, its ability to move from place to place by swimming, are all interesting features; but, when it is ascertained to be the first creature in the entire Animal Kingdom in which a true nervous system is to be found, then it becomes doubly interesting.
This protozoan has been a favorite subject for study with microscopists, but Professor Clark of Harvard was the first observer to note and call attention to its nerve-supply. Says he in his note calling attention to this discovery:—
"The digestive and circulatory systems are the only parts of the organization essential to life that are known to investigators; but recently I have been led to believe that I have discovered the nervous system, or at least a part of it, and that too in the very region of the body where there is the most activity, and therefore more likely than elsewhere to have this system most strongly developed. Immediately within the edge of the disk (bell) there runs all around a narrow faint band, which lies so close to the surface that it is difficult to determine precisely that it is not actually superficial. From this band there arise, at nearly equal distances all round, about a dozen excessively faint thin stripes, which converge in a general direction toward the mouth."[30]
This band Professor Clark very correctly, as I believe, assumes to be a part of Stentor's nervous system; for, with a medium high-power lens (×500) I have been able to make out ganglionic enlargements both in the circular band and in the stripes. These ganglia are the brain of this infusorian. When the animalcule is stained with eosin, the nervous system can very readily be made out and followed throughout all of its ramifications.
On one occasion, while I was studying the contractile vesicle (heart) of one of these animalcules, I saw it evince what seemed to me to be unquestionable evidences of conscious determination.