So records were kept, as I indicated, of this particular event and a few weeks later, the same event occurred in another culture. I don't recall the precise number of cultures in which this event of... this event occurred. And the event was that the cells looked bigger. There were many fewer mitotic figures, that is fewer cells were dividing. And as the weeks went by in those particular cultures, there was no division occurring at all. But the cells didn't die, they continued to metabolise. That's an important observation. And we knew that because the media in which cells are generally grown contained a pH indicator. And neutral pH, which is their favourite pH condition, produces a colour that's rosy red and when they're metabolising, that neutral media becomes acidic and the culture turns orange and then yellow. And although the cells in these cultures that weren't dividing seemed to be metabolising because the media turned yellow, we had to change the media every week or two now, although we couldn't subculture them because they weren't dividing any longer, the... it was apparent to us that they were not dead, just sitting there metabolising.

I can't recall with accuracy the number of times we saw that... those events in... in cultures from individual embryos, but the number got increasingly greater and looking at my records, I then realised an important point and that was that the cultures that had stopped dividing – let's say from three or four of the 20 that were in the incubator – were the oldest ones. That is they were ones that were derived from embryos received about ten months or so roughly prior to this event. The other ones, received a week ago, a month ago, three months ago, were happy and it's important to say that the same technician was culturing these weekly, or semi-weekly and the same pool of glassware obtained from our storage area was used, so... and the same pool of culture media. So it became obvious that there was something about a cell culture that was older producing this effect.