This is a typical F. sultana colony. The round polyps are clearly seen.
This photo shows a somewhat larger colony growing on the side of a rock.
Often F. sultana branches split at the end, so two polyps extend close to eachother.
For whom observes well there is a worm to be seen crawling in the middle of the colony.
This photo shows the worm species in more detail. It is Stylaria lacustris. I also saw this species in P. fruticosa clonies. Observation both in situ and under a microscope have not convinced me that the worm eats zooids. It crawls fanatically through the colony searching for food, but does not seem to hunt zooids aggressively. The zooids do retract if the worm touches them.
In the P. fruticosa page the worm is shown photographed under a microscope. /p>
The next picture shows a detail of the typical fredericella polyp.
The following photo shows how large a F. sultana colony can grow. This one was about 10 x 5 cm and significantly larger than the colonies i usually find. It is known from literature that F. sultana can grow to even larger colony size, provided good circumstances. For example there are instances where F. sultana was growing so massively inside water mains that public water supply was endangered (in the beginning of the 20th century.
This picture shows some zooids in detail. Please note that F. sultana zooid walls are far more covered in debris than P. fruticosa whom it resembles mosts.