What did Pip see on Miss Havisham’s table on her birthday?

From the text:

"An epergne or centrepiece of some kind was in the middle of this cloth; it was so heavily overhung with cobwebs that its form was quite undistinguishable; and, as I looked along the yellow expanse out of which I remember its seeming to grow, like a black fungus, I saw speckled-legged spiders with blotchy bodies running home to it, and running out from it, as if some circumstances of the greatest public importance had just transpired in the spider community."