"Ontogeny recapitulates phylogeny" is the idea that as an organism starts to take shape in the womb (/eggshell, whatever) it goes through the same stages in development as the species did as it was evolving: this view once held some sway in the scientific community, until it was contradicted by observation. In other words, once we were capable of seeing what actually happens as a fertilized egg develops, this somewhat over-simplistic view was discarded: what I like most about science is that it is by its nature open to argument about whether it might have got things wrong...

A rather over-long intro to a short song, but I figured that not many people would have a clue what I was talking about... I sometimes wonder if I do :-)