The Driesch Phenomenon: Long a Holy Grail of Developmental Biology.
Different-sized Dictyostelium slugs maintain about the same ratios of length to width, and the same proportionality of stalk height/spore mass volumes. Big slugs form taller fruiting bodies, etc. By what mechanism?(s)?
As Hans Driesch discovered (1890s), separating the first 4 cells of starfish
(or other echinoderm) cleavage-stage embryos results in 1/4 sized larvae.
Sticking two one-cell stages together results in a double-sized larva.
By what mechanism(s?) do early stages of sea urchin embryos adjust the sizes of their organs in proportion? Biologists have never gotten their minds around these questions. Can Molecular Biology get closer to answers?
Please try to invent possible causes; And experiments to test them.
Many biologists confuse "positional information" with "prepatterns."
Don't bother to read this book about "purposefulness of developing embryos.
But philosophizing need not always be empty. Embryology's problem of shape "regulation" is a mega-problem, or meta-problem, comparable to "How can nerve networks learn, remember or think", "How does music work", etc.