A fun one! This project was for a long time customer with a good sense of humor. Dr. Mark Voelker was working with the time-honored Planaria in experiments to slow metabolic rates. He wanted to "corral" his worms and designed the glassware shown at the right for that purpose. 
The palace sits on the bottom of a larger aquarium, and water, oxygen, and nutrients are able to flow through the large porosity fritted bottom. He can place a lid on top to keep the residents in place (Planaria Prison?).
But there was an unforseen problem, not unusual with glass prototypes. The frit attracted other residents as well, and grew quite moldy over time. Talk about Green Business.....

Solution? Remodel! We were able to modify the glass to accomodate an extra "bedroom" so that the "rooms" could be cleaned periodically

Dr. Voelker writes;
Thanks for your timely production of my 'Planaria Palace', a corral to hold planaria flatworms in my 5 gallon aquarium. This latest item is just one of many custom pieces of scientific glass I have purchased from you over the years, and they all have turned out really well. Even if I need to change the design in the middle of the job, you work with me to get it made right!
It's always a pleasure working with you and your crew, who take the time to listen to my technical requests, provide design advice, and generally interact with me as fellow human beings should. You always do a great job, even for small one-piece customers like me, and for a reasonable price too! That's why I keep coming back. And you just make such beautiful, cool stuff!
May you live long, and prosper!

Best regards, Mark A. Voelker, PhD