species of insects, e.g. ants. Often, when the nervous systems appear precisely similar, we find that the mental traits as manifested in the actions of the animals differ vastly. Changes in nervous tissue seem, magnified a thousandfold when examined through their psychical concomitants. But however obscure and difficult the subject, two facts may be made out: (1) That acquired psychical changes are never transmitted, and (2) that, just as regards their corporal structures, so as regards their mental traits, the action of Natural Selection has been to develop in higher animals an immense power of varying, of individually acquiring variations, whereby the organism is brought into completer harmony with its complex environment.
In animals low in the scale, such as the coelenterates, almost all the reactions to stimulation from the environment are of the kind known as reflex. In them Natural Selection has brought about the evolution of particular reactions, whereby particular and generally oft-recurring events in the simple environment are provided against; the power of making these appropriate responses to particular stimuli being obviously inborn and transmissible. Higher in the scale, occurs that kind of response to stimulation which is known as Instinct, and which Mr. Spencer has defined as "compound reflex action," but which Professor Romanes rightly insists is something more—is action into which has been imported the element of consciousness.
It may be defined as "the faculty which is concerned in the conscious adaption of means to ends," by virtue of inborn inherited knowledge and ways of thinking and acting. For example, the young alligator or the young turtle instinctively seek the water on emerging from the egg, i.e. they seek it by virtue of their inborn and inherited knowledge and ways of thinking and acting. Instinct also is clearly transmissible.
