I listened enthralled to Tracy Sonneborn developing the argument with his students that, particularly the famous kappa particles, or the genes which encoded them, might be part of the paramecium and it was somehow a model for cellular differentiation in the human body. And at the end of the year, I was leaving Indiana and it was still all up in the air. Delbruck at Cold Spring Harbour had proposed to Tracy that all his work on the killer particles and on the related project of- there was variants in the cilia. The proteins are make up cilia which behaved in roughly the same way, could be not cytoplasmic inheritance, but rather stable circuits of genes being turned on and turned off, and the turning off turned on, ultimately worked round to stabilise cellular inheritance. And, in fact, Delbruck was proposing what now everybody thought. Tracy was shaken to the core by that and he talked about it with us very frankly and he said, I don't have a good argument against Delbruck, but I want to go on- I'm going to go on, for the time being, looking for cytoplasmic inheritance, and then I left. Sadly, within a very short time, two or three years, Ruth Dipple turned up DNA in the kappa particles so there was no doubt from then on that those were bacterial contaminants inside the paramecium. Well, that's biology. Things don't work out the way you'd expected it. What I- I liked Sonneborn enormously and I know that he found me difficult and he didn't quite understand what I was trying to do. But he let me write a paper on my own. And later, when I came- he was very- quite soon he became very ill and died. But I met him once more in Europe, in England actually, and he did two things. He brought me a present from America of a nice tie. I wasn't much into wearing ties, but I was touched to the core by that, being given a present. I don't think he'd ever given a present to anybody before. And the second thing, he then made his own speech, and he said, that what I had been talking to him about was what was now the main thing in his mind. So I don't think that- I think he was probably exaggerating a lot, but I thought- I was touched to the core when he said that I'd been an influence on him, because he was an older man and I deeply respected him.