That confused me too. In the SC1 manual they're basically men with mushroom heads whereas, well, you all know what they look like in SC2.
To continue... does anyone remember if it's mentioned anywhere what the Podship is? Is it a Mycon or some sort of living entity or something constructed? Also, apart from Deep Children, is any other form of Mycon every mentioned?
These are all questions that plague my waking thoughts. Okay, really, to much sugar for me now