Lucretius, De Rerum Natura
William Ellery Leonard, Ed.

     Now come, and next hereafter apprehend
What sorts, how vastly different in form,
How varied in multitudinous shapes they are-
These old beginnings of the universe;
Not in the sense that only few are furnished
With one like form, but rather not at all
In general have they likeness each with each,
No marvel: since the stock of them's so great
That there's no end (as I have taught) nor sum,
They must indeed not one and all be marked
By equal outline and by shape the same.
     . . . . . .
Moreover, humankind, and the mute flocks
Of scaly creatures swimming in the streams,
And joyous herds around, and all the wild,
And all the breeds of birds- both those that teem
In gladsome regions of the water-haunts,
About the river-banks and springs and pools,
And those that throng, flitting from tree to tree,
Through trackless woods- Go, take which one thou wilt,
In any kind: thou wilt discover still
Each from the other still unlike in shape.
Nor in no other wise could offspring know
Mother, nor mother offspring- which we see
They yet can do, distinguished one from other,
No less than human beings, by clear signs.
Thus oft before fair temples of the gods,
Beside the incense-burning altars slain,
Drops down the yearling calf, from out its breast
Breathing warm streams of blood; the orphaned mother,
Ranging meanwhile green woodland pastures round,
Knows well the footprints, pressed by cloven hoofs,
With eyes regarding every spot about,
For sight somewhere of youngling gone from her;
And, stopping short, filleth the leafy lanes
With her complaints; and oft she seeks again
Within the stall, pierced by her yearning still.
Nor tender willows, nor dew-quickened grass,
Nor the loved streams that glide along low banks,
Can lure her mind and turn the sudden pain;
Nor other shapes of calves that graze thereby
Distract her mind or lighten pain the least-
So keen her search for something known and hers.
Moreover, tender kids with bleating throats
Do know their horned dams, and butting lambs
The flocks of sheep, and thus they patter on,
Unfailingly each to its proper teat,
As nature intends. Lastly, with any grain,
Thou'lt see that no one kernel in one kind
Is so far like another, that there still
Is not in shapes some difference running through.
By a like law we see how earth is pied
With shells and conchs, where, with soft waves, the sea
Beats on the thirsty sands of curving shores.
Wherefore again, again, since seeds of things
Exist by nature, nor were wrought with hands
After a fixed pattern of one other,
They needs must flitter to and fro with shapes
In types dissimilar to one another.