The flask icons are there to help you identify the animals you don't have in your zoo, or for which you do not have a pair. The number of flasks indicates the number of different animals that you can get from the experiment.

There are three types of flask icons:

• An empty flask indicates that a particular experiment has never been run.
• A half-filled flask indicates that the experiment has been run, but you haven’t collected the full species family.
• A full flask indicates that the experiment has been run and you’ve collected the full species family.