Not "layers" as such, more "carrier".
Research the life cycle, you'll find this in more details but;
You'll notice the females have a more "skirted" abdomen, hangs lower around the rear "legs" than on the males. They also have a "saddle" (looks like the sort you would place on a horse) that starts just behind their head and extends backwards. This can start green/yellow and starts to get bigger. Once the eggs are finished in the saddle, the female (for lack of better words) "gives birth" to these eggs, but continues to hold them under the above mentioned "skirt" between her legs until they are ready to hatch. She will constantly waft water over the eggs with the hind "legs" until they are ready. Its said that a female can tell which of the eggs are hatching by feel, even if hundreds being carried, and will "kick" the hatching ones from the back of her abdomen. At this point the babies will immediately look for dense cover to avoid predation.
In short, what you have in the coner of your tank may be eggs, but theyre probably not from shrimp. If they are and have been "dropped", as Al said, they wont survive. Normally happens when they are too yound, predated on or just generally stressed.
