There were lots of arguments and discussions in the literature as to how we would ever get an explanation of development and there were lots of schools of thought about this. And one of the problems was relating all of this at that level, to what we felt had to be molecular information… I mean, in the end genes make proteins and proteins have to do something, so what is it they are doing? Well, of course they could be synthesising and destroying morphogenetic chemicals. So there was a great search for these morphogenetic chemicals. And some... in some organisms things that behaved as though they were morphogenetic chemicals were to be... were found. And many people didn't believe these, that there would be gradients of diffusible compounds, largely on the grounds that if they existed the biochemists would have already found them. Since the biochemists hadn't found them they can't exist. And I think that there was a lot of confusion about... that diffusion would be consistent with the results of the experiment, but it's not necessary that things should travel necessarily by diffusion, and need not necessarily be small molecules like this. During this time we got very interested in a series of experiments that had been done on... which seemed to... to give the most challenging problem in all of this, which was the wiring up of the retina, to, in lower organisms, the tectum. Everybody knew that the eye was projected onto the tectum in a very careful manner, so that each part got projected onto a certain region, and so the geometry was perfectly represented. But what was amazing was that there were experiments in frogs that if you cut these projections and let them regenerate, they could regenerate right to the... to the correct place and rewire the nervous system appropriately. Now, when you think about that... that said there had to be some kind of code of specification. And one of the questions at the time was: was there a code of recognition in the nervous system? If we have to make so many synaptic connections, how was this encoded?
