I knew about Placozoa, but not about the spherical propagules; just wondered if they might exist, and Google tells me they do!
Now for the question.
They are shell-less, lunged hermaphrodites which have functional eyes on their backs. The majority of species live in mangrove habitats in and around Indonesia, but there are species which live on rocky shores in New Zealand, South Africa, California and Cornwall, where they are active grazers when the tide goes out. What are they?