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Wow, amazing film! If only my french was a bit better...

Sorry, I missed to say there's no real wet connection between the pond and the place I found the object. They're separated by a small (and dry) path. So an aquatic gastropod would be unlikely, I think.

Nevertheless it looks quite similar to the white thing, that Tony identified as slug eggs here: http://www.diptera.info/forum/viewthread.php?thread_id=69355

But I really wonder which kind of (non-aquatic) snail or slug produces such an egg cluster. I can only find pictures of eggs, which are separated from each other. This isn't a distinctive character of aquatic gastropods, is it?