Yes, most of your clutch probably dried out-otherwise it would be swarming with baby snails. The snails that were in the center of the clutch probably survived because they were the moist ones. You want to keep the clutch DRY but in humid conditions.
This is what I did:
After 24 hours (to allow the clutch to harden and not smoosh when you remove it), remove the clutch from wherever it was laid in the tank. I set mine on a piece of filter media. Whatever you set it on should be porous to allow air flow under the clutch, and you also don't want something solid that will allow moisture to collect under the clutch, because that will drown all of the bottom eggs. Set your clutch on say a piece of filter material.
Then set that upon a damp, but not soaking wet paper towel. Place the towel, then the filter media, and then the clutch ontop of the filter media inside a ziploc bag. Place the ziplock bag on top of a heating pad on the lowest setting. You want the bag inside to remain very humid, but you dont want to directly make your clutch wet. Make sure to have the ziploc bag full of air as to allow circulation. Open the bag everyday and put new air in.
When you get a few days before the snails are due to hatch, transfer the clutch and float it on something above where you plan on raising the baby snails. For me, I floated my clutches above a breeder net in my full size tank.
Here's a photo of mine floating:
That way I was sure that they hatched into the proper environment with plenty of food, and I was sure that they would not be vaccumed up during my weekly cleanings. Just remember baby snails require pristine water conditions, and a good supply of food, and reccommended calcium supplements which will make them grow up fast and strong.
I never had a clutch that didn't hatch. Before you know it, you will be crawling with baby snails.
Viola!
Baby snails.
