----- Original Message -----From: [log in to unmask] href="mailto:[log in to unmask]">Brenner, BobTo: [log in to unmask] href="mailto:[log in to unmask]">[log in to unmask]Sent: Monday, January 23, 2006 8:02 PMSubject: Re: FW: Re: Effects of collecting shells from beaches, and change s in the numbers of shells on beachesFor whatever this is worth....Some years ago, I noticed that 23 of 25 cockle shells my kids gathered from Casey Key beach were, I believe the left valves. I mentioned this to one of my co-workers nad he said that he had done a short paper on that phenomennon while an undergraduate. The jist was that the valves spin in opposite directions when caught up in an alongshore current. He painted several of them, dropped them in the "first trench" and spent a few days watching them. Very soon, half of them would disappear into deeper water while the others remained. When the tide changed, the direction of the current reversed and the effect was the same - but the valves that remained in the first scenario spun into deeper water while the others remained.I've often wondered whether the ratio changes from summer to winter - assuming that the alongshore di8rection changes.