=Racial Development.= The purpose of this chapter is to make some inquiry concerning the origin of the race and of the individual. In doing this, it is necessary for us first of all to fix in our minds the idea of causality. According to the view of all modern science, everything has a cause. Nothing is uncaused. One event is the result of other previous events, and is in turn the cause of other events that follow. Yesterday flowed into to-day, and to-day flows into to-morrow. The world as it exists to-day is the result of the world as it existed yesterday. This is true not only of the inorganic world--the world of physics and chemistry--but it is true of living things as well. The animals and plants that exist to-day are the descendants of others that lived before. There is probably an unbroken line of descent from the first life that existed on the earth to the living forms of to-day. Not only does the law of causality hold true in the case of our bodies, but of our minds as well. Our minds have doubtless developed from simpler minds just as our bodies have developed from simpler bodies. That different grades and types of minds are to be found among the various classes of animals now upon the earth, no one can doubt, for the different forms certainly show different degrees of mentality. According to the evidence of those scientists who have studied the remains of animals found in the earth's crust, there is a gradual development of animal forms shown in successive epochs. In the very oldest parts of the earth's crust, the remains of animal life found are very simple. In later formations, the remains show an animal life more complex. The highest forms of animals, the mammals, are found only in the more recent formations. The remains of man are found only in the latest formations. Putting these two facts together--(1) that the higher types of mind are found to-day only in the higher types of animals, and (2) that a gradual development of animal forms is shown by the remains in the earth's crust--the conclusion is forced upon us that mind has passed through many stages of development from the appearance of life upon the earth to the present time. Among the lower forms of animals to-day one sees evidence of very simple minds. In amoebas, worms, insects, and fishes, mind is very simple. In birds, it is higher. In mammals, it is higher still. Among the highest mammals below man, we see manifestations of mind somewhat like our own. These grades of mentality shown in the animals of to-day represent the steps in the development of mind in the animals of the past.