and stronger as time goes on.  Some yield more readily to the urge, and such become the parents of possible higher forms.  “Many are called, but few are chosen,” and so matters move along slowly from generation to generation, a few forms serving to carry on the evolutionary urge to their descendants.  But is always the Evolutionary Urge of the imprisoned Mind striving to cast aside its sheaths and to have more perfect machinery with which, and through which, to manifest and express itself?  This is the difference between the “Evolution” of Modern Science and the “Unfoldment” of the Yogi Teachings.  The one is all material, with mind as a mere by-product, while the other is all Mind, with matter as a tool and instrument of expression and manifestation.

As we have said in this lesson—­and as we shall point out to you in detail in future lessons—­accompanying this evolution of bodies there is an evolution of “souls” producing the former.  This evolution of souls is a basic principle of the Yogi Teachings, but it is first necessary that you acquaint yourselves with the evolution of bodies and forms, before you may fully grasp the higher teachings.

Our next lesson will be entitled “The Ascent of Man,” in which the rise of man—­that is, his body—­from the lowly forms of the vertebrates is shown.  In the same lesson we shall begin our consideration of the “evolution of souls.”  We trust that the students are carefully studying the details of each lesson, for every lesson has its part in the grand whole of the Teachings.

THE EIGHTH LESSON

THE ASCENT OF MAN.

In our last lesson we led you by successive steps from the beginnings of Life in living forms up to the creatures closely resembling the family of vertebrates—­the highest family of living forms on this planet.  In this present lesson we take up the story of the “Ascent of Man” from the lowly vertebrate forms.

The large sub-family of forms called “The Vertebrates” are distinguished from the Invertebrates by reason of the former possessing an internal bony skeleton, the most important feature of which is the vertebra or spinal column.  The vertebrates, be it remembered, possess practically the same organs as the lower forms of life, but differ from them most materially by the possession of the internal skeleton, the lower forms having an external or outside skeleton, which latter is merely a hardening of the skin.

The flexibility of the vertebra creates a wonderful strength of structure, combined with an ease of movement peculiar to the vertebrates, and which renders them the natural forms of life capable of rapid development and evolution.  By means of this strength, and ease, these forms are enabled to move rapidly in pursuit of their prey, and away from their pursuers, and also to resist outside pressure or attack.  They are protected in a way similar to the invertebrates having shells, and yet have the additional advantage of easy movement.  Differing in shape and appearance as do the numerous members of the sub-family of vertebrates, still their structure is easily seen to spring from a single form—­all are modifications of some common pattern, the differences arising from the necessities of the life of the animal, as manifested through the desire and necessities of the species.