First lecture in Vertebrate Embryology: Jan 9, 2013, Albert K. Harris


Textbook: Lewis Wolpert and Cheryll Tickle
Principles of Development, 4th Edition

This is currently the clearest, most analytical text available. It summarizes coherent ideas about how embryos work. Personally, I disagree with many of Wolpert's ideas. He is at one extreme and I am at another extreme.

By learning BOTH, you will gain better understanding of both the facts and the debates going on in this subject.

The most accurate and complete textbook on our subject is the UNABRIDGED edition of "The Molecular Biology of the Cell" by Bruce Alberts, etc, etc, 3rd or 4th edition. But that book is too huge, too expensive and covers so many additional subjects. If you own a copy, don't sell it! It's a gold mine of true facts, fairly presented. It could help you understand this course better & will help you in med school.


Scientific progress is made by disagreements between different researchers and theoreticians.

If everybody agreed, that would mean progress had stopped.
That won't happen until everything is understood.

I used to be a good friend of both Lewis Wolpert and Cheryll Tickle. She was a post-doctoral fellow (from England) in the laboratory where I was just finishing my PhD and getting ready to move to England, to the University where she had been an undergraduate. Each of us learned a lot from each other about these strange new countries, where we would live.

Lewis Wolpert befriended me and my wife during our years in England, for which we are indebted.

On the other hand, Wolpert and I have always interpreted embryology very differently.

He was the strongest advocate of the "polar relaxation" theory of the cause of cytokinesis (cleavage). I was one of those who proved cleavage furrows really are induced be "polar stimulation". (This course will include a brief summary of the evidence on both sides & what we can learn from it.)

Wolpert is best known in science for proposing the (misguided) concept of "Positional Information" (that I have published many papers arguing against.)

My own major discovery has been that tendons, skeletal muscles, organ capsules etc. can be directly formed by mechanical "traction forces", with nothing like a blue print. Wolpert has disparaged my interpretations of my time-lapse videos of collagen & muscle rearrangement. In this textbook, the most he will admit is that muscle formation is "autonomous" (in the sense of being caused by some local effect of bones, which he prefers to think is a chemical signal)

Again and again, the book is going to claim that embryonic structures are created by one mechanism, and I am going to argue in favor of some theory that is almost the opposite.

You are going to need to learn

    #1: That scientists don't yet really agree on that subject
    (Progress is still going on. Breakthroughs are still available for you!)

    #2) Wolpert's theories (which some standardized tests think are true)

    #3) My counter-arguments, and alternative theories.

Please invent experiments that could prove whether he is right or whether I am right!
That's how scientists make progress.


Egg cell = oocyte + sperm = spermatozoan → → Trillions of differentiated cells → → Organs & tissues

Small, simple, homogeneous → → → → Large, complex, geometrically complicated

DNA base sequences → → →Anatomical shapes, geometrical arrangements of cells


I will begin the course by describing embryos of mammals, before continuing with embryos of sea urchins, amphibians, teleost fish, birds & reptiles.

(Diagrams of all these are combined in one big nifty diagram that I drew so you could memorize it.)

Please ask lots of questions.
We have plenty of time.

There is no such thing as a dumb question.

The other students will be secretly grateful to you for asking.





back to syllabus