It started out sort of slowly, but that may just be because my eyes tend to glaze over when people start talking about certain aspects of Biology. Once he got some of the technical stuff out of the way it was incredibly interesting. He did a great job out of not making Mutants into fetishized creepy attractions; focusing instead on the development of the fetus and the fantastic beauty and complexity therein. He also provided a lot of stuff on the connection between figures of mythology (the cyclops, giants, mermaids, etc) and the real-life mutated counterparts that may have inspired them. Also, his stuff on death as a genetic disorder that afflicts all living things and will eventually be "cured" is rad.
Mutants: On Genetic Variety and the Human Body