It just gets a little bit dry, I try to germinate into a paper towel and then place the taproot into the soil at such an angle that it will need to drag itself out itself out the soil leaving behind the empty shell in the medium. Often times if the shell is exposed to air it drys very fast. Keep a humidity dome on until you can see the 2 coteloydon then take off dome immediately. This should keep it moist enough, if you need to you can very gently pry open the partially opened shell finger nails or tweezers but I found tweezers to be unreliable. This is not ideal but I've saved many wee seeds.