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Sorry, I was close ...
I have been guided by the size and the image of wet moss, where the egg mass is located
So far from the pond would be impossible, and after all Physa acuta need very clean water
I believe that number of eggs/cluster depends on genus and on living conditions for aquatic snails. We could say that they are characteristics but by experience I
often see variations in the number of eggs in a cluster but rarely variations for the size of the eggs. I don't know for non aquatic organisms.
SDS