For anybody capable of an emotional response to it, any view of a developing organism should give birth to a feeling of amazement and even admiration, whether this development is seen directly, or in the form of a time lapse film, or even if mentally reconstructed from a series of static images. We ask ourselves how such seemingly primitive eggs or pieces of tissue, without any obvious intervention from outside, so regularly transform themselves into precisely constructed adult organisms. If we try to formulate what amazes us most of all about development, the answer will probably be that it...