“The sixth, and of creation last, arose
  With evening harps and matin, when God said,
  ’Let tine earth bring forth soul living in her kind,
  Cattle and creeping things, and beast of the earth,
  Each in their kind!’ The earth obeyed, and, straight
  Opening her fertile womb, teemed at a birth. 
  Innumerous living creatures, perfect forms,
  Limbed and full-grown.  Out of the ground uprose,
  As from his lair, the wild beast, where he wons
  In forest wild, in thicket, brake, or den: 
  Among the trees in pairs they rose, they walked;
  The cattle in the fields and meadows green;
  Those rare and solitary; these in flocks
  Pasturing at once, and in broad herds upsprung. 
  The grassy clods now calved; now half appears
  The tawny lion, pawing to get free
  His hinder parts—­then springs, as broke from bonds,
  And rampant shakes his brinded mane; the ounce,
  The libbard, and the tiger, as the mole
  Rising, the crumbled earth above them threw
  In hillocks; the swift stag from underground
  Bore up his branching head; scarce from his mould
  Behemoth, biggest born of earth, upheaved
  His vastness; fleeced the flocks and bleating rose
  As plants; ambiguous between sea and land,
  The river-horse and scaly crocodile. 
  At once came forth whatever creeps the ground,
  Insect or worm.”

There is no doubt as to the meaning of this statement, nor as to what a man of Milton’s genius expected would have been actually visible to an eyewitness of this mode of origination of living things.

The third hypothesis, or the hypothesis of evolution, supposes that, at any comparatively late period of past time, our imaginary spectator would meet with a state of things very similar to that which now obtains; but that the likeness of the past to the present would gradually become less and less, in proportion to the remoteness of his period of observation from the present day:  that the existing distribution of mountains and plains, of rivers and seas, would show itself to be the product of a slow process of natural change operating upon more and more widely different antecedent conditions of the mineral framework of the earth; until, at length, in place of that framework, he would behold only a vast nebulous mass, representing the constituents of the sun and of the planetary bodies.  Preceding the forms of life which now exist, our observer would see animals and plants not identical with them, but like them:  increasing their differences with their antiquity, and at the same time becoming simpler and simpler; until, finally, the world of life would present nothing but that undifferentiated protoplasmic matter which, so far as our present knowledge goes, is the common foundation of all vital activity.

The hypothesis of evolution supposes that in all this vast progression there would be no breach of continuity, no point at which we could say “This is a natural process,” and “This is not a natural process”; but that the whole might be compared to that wonderful process of development which may be seen going on every day under our eyes, in virtue of which there arises, out of the semifluid, comparatively homogeneous substance which we call an egg, the complicated organization of one of the higher animals.  That, in a few words, is what is meant by the hypothesis of evolution.