But this element of consciousness is one which it is exceedingly difficult to detect in our analysis, and yet upon it our classification and the psychic position of an animal must to a great extent depend.  The amoeba contracts when pricked, jelly-fishes swim toward the light, the earthworm, “alarmed” by the tread of your foot, withdraws into its hole.  Are these and similar actions reflex or instinctive?  A grain of consciousness preceding an action which before has been reflex changes it into instinct.  Mr. Romanes, probably correctly, regards them as purely reflex.  We must, I think, believe that these actions result in consciousness even in the lowest forms.  The selection and attainment of food certainly looks like conscious action.  Probably all nerve-cells or nervous material were originally, even in the lowest forms, dimly conscious; then by division of labor some became purely conductive, others more highly perceptive.  The important thing for us to remember in our present ignorance is not to be dogmatic.

Furthermore, the gain of a grain of consciousness of the adaptation of certain means to special ends changes instinctive action into intelligent, and its loss may reverse the process.  Fortunately we have found that in so far as actions, even instinctive, are modified by experience, they are becoming to that extent intelligent.  This criterion of intelligence seems easily applied.  But this profiting by experience must manifest itself within the lifetime of the individual, or in lines outside of circumstances to which its ordinary instincts are adapted, or we may give to individual intelligence the credit due really to natural selection.  We must be cautious in our judgments.

These reflex actions are performed independently of consciousness or will.  Consciousness may, probably does, attend the selection and grasping of food; but most of the actions of the body will go on better without its interference.  It is not yet sufficiently developed, or, so to speak, wise enough to be intrusted with much control of the animal.

Among higher worms cases of instinct seem proven.  Traces of it will almost certainly be yet found much lower down.  Fresh-water mussels migrate into deeper water at the approach of cold weather.  And if the clam has instincts, there is no reason why the turbellaria should not also possess them.  But all higher powers develop gradually, and their beginnings usually elude our search.  Along the line leading from annelids to insects instinct is becoming dominant.  A supraoesophageal ganglion has developed, and has been relieved of most of the direct control of the muscles.  Very good sense-organs are also present.  From this time on consciousness becomes clearer, and the brain is beginning to assert its right to at least know what is going on in the body, and to have something to say about it.  Still, as long as the actions remain purely instinctive the brain, while conscious, is governed by heredity.  The animal does as its ancestors always have.  It does not occur to it to ask why it should do thus or otherwise, or whether other means would be better fitted to the end in view.  It acts exactly like most of the members of our great political and theological parties.  And until the animal has a better brain this is its best course and is favored by natural selection.