thinking, moral, religious person, like man?  “That is not first which is spiritual, but that which is natural (animal, sensuous); and afterward that which is spiritual.”  First, in order of time, must come the body, and then the mind and spirit shall be enthroned in it.  The little knot of nervous material which forms the supra-oesophageal ganglion is so small that it might easily escape our notice; but it is the promise of an infinite future.  The atom of nervous power shall increase until it subdues and dominates the whole mass.

CHAPTER III

WORMS TO VERTEBRATES:  SKELETON AND HEAD

In tracing the genealogy of any American family it is often difficult or impossible to say whether a certain branch is descended from John Oldworthy or his cousin or second cousin.  In the latter cases to find the common ancestor we must go back to the grandfather or great-grandfather.  The same difficulty, but greatly enhanced, meets us when we try to make a genealogical tree of the animal kingdom.  Thus it seems altogether probable that all higher forms are descended from an ancestor of the same general structure and grade of organization as the turbellaria, although probably free swimming, and hence with somewhat different form and development, especially of the muscular system.  It seems to me altogether probable that all, except possibly Mollusca, are descended from a common ancestor closely resembling the schematic worm last described.  Some would, however, maintain that they diverged rather earlier than even the turbellaria; others after the schematic worm, if such ever existed.  As far as our argument is concerned it makes little difference which of these views we adopt.

From our turbellaria, or possibly from some even more primitive ancestor, many lines diverged.  And this was to be expected.  The coelenterata, as we saw in hydra, had developed rude digestive and reproductive systems.  The higher groups of this kingdom had developed all, or nearly all, the tissues used in building the bodies of higher animals—­muscular, reproductive, connectile, glandular, nervous, etc.  But these are mostly very diffuse.  The muscular fibrils of a jelly-fish are mostly isolated or parallel in bands, rarely in compact well-defined bundles.  The tissues have generally not yet been moulded into compact masses of definite form.  There are as yet very few structures to which we can give the name of organs.  To form organs and group them in a body of compact definite form was the work pre-eminently of worms.  The material for the building was ready, but the architecture of the bilateral animal was not even sketched.  And different worms were their own architects, untrammelled by convention or heredity, hence they built very different, sometimes almost fantastic, structures.