From 2speccers2tools wiki

After many millions of years, the lego cells and lego cell joint parts finally ended up making patterns that were more than just giant blocks randomly stuck together by lines of joint parts. These small colonies of lego cells have a relatively conserved shape, with a wide base and 3-6 ‘arms’ with joints at their bases. The lego cells in these ‘fingers’ usually remain open on one side to catch as many food particles as possible, only closing up when danger arrives. New boinicles are created from hardy, brownish spores released from the tip of each arm, which float through the water column until they settle on the seafloor. The spore then grows into the wide base, which soon sprouts a group of arms. Due to how long they have been in symbiosis, the lego cell and lego cell joint part portions of the organism have essentially merged genetically, with each cell type containing the full genome of the other, allowing the lego cells to create new joint parts all by themselves and vice versa.