One of the best understood morphogenetic systems is the patterning along the future head to tail (antero-posterior) axis of the fruit fly Drosophila melanogaster. The development of Drosophila is particularly well studied, and it is representative of one major class of insects, called insecta. Other multicellular organisms sometimes use similar mechanisms for axis formation, although the relative importance of signal transfer between the earliest cells of many developing organisms is greater than in the ex ...
