It is there as the oak is inside the acorn.
A fine transparent cushion limits the free edge of the embryo wing and the embryo wing-case.

Under a powerful microscope we can perceive therein a few doubtful lineaments of the future lace-work.

This might well be the factory in which life will shortly set its materials in movement.

Nothing more is visible; nothing that will make us foresee the prodigious network in which each mesh must have its form and place predetermined with geometrical exactitude.
In order that the organisable material can shape itself as a sheet of gauze and describe the inextricable labyrinth of the nervuration, there must be something better and more wonderful than a mould.

There is a prototypical plan, an ideal pattern, which imposes a precise position upon each atom of the tissue.