Given the task definition and input, reply with output. In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

One group in this phylum probably descended from heteractinids, which went extinct during the Paleozoic Era. This phylum's immune response includes the accumulation of grey cells. In organisms in this phylum, totipotent amoebocytes allow for reproduction and the distribution of nutrients digested by current-producing choanocytes. Those choanocytes, with epidermal pinocytes, bound a gelatinous matrix known as the mesohyl, which separates the two layers of organisms in this phylum. The asconoid and syconoid body forms also feature an osculum along with spicules produced by sclerocytes. For 10 points, name this invertebrate phylum of sessile, suspension-feeding animals commonly known as sponges.
Science