superfluous nourishment becomes
an homogeneous body, which is then changed by successive transformations
into an animal.

Digby is frankly deterministic in his description of embryonic
development:

Take a beane, or any other seede, and putt it into the earth, and
lett water fall upon it; can it then choose but that the beane must
swell? The beane swelling, can it choose but breake the skinne? The
skinne broken can it choose (by reason of the heate that is in it)
but push out more matter, and do that action which we may call
germinating.... Now if all this orderly succession of mutations be
necessarily made in a beane, by force of sundry circumstances and
externall accidents; why may it not be conceived that the like is
also done in sensible creatures; but in a more perfect manner....
Surely the progresse we have sett downe is much more reasonable,
then to conceive that in the meale of the beane, are contained in
litle, severall similar substances.... Or, that in the seede of the
male, there is already in act, the substance of flesh, of bone, of
sinewes, of veines, and the rest of those severall similar partes
which are found in the body of an animall; and that they are but
extended to their due magnitude, by the humidity drawne from the
mother, without receiving any substantiall mutation from what they
were originally in the seede. Lett us then confidently conclude,
that all generation is made of a fitting, but remote, homogeneall
compounded substance: upon which, outward Agents working in the due
course of nature, do change it into an other substance, quite
different from the first, and do make it lesse homogeneall then the
first was. And other circumstances and agents, do change this
second into a thirde; that thirde, into a fourth; and so onwardes,
by successive mutations (that still make every new thing become
lesse homogeneall, then the former was, according to the nature of
heate, mingling more and more different bodies together) untill
that substance be produced, which we consider in the periode of all
these mutations....[10]

Digby thus makes a good statement of epigenetic development. He
attempts, without success, a physiochemical explanation of the
mechanisms of development, finally admitting:

I persuade my selfe it appeareth evident enough, that to effec