Which of the following is a unique feature of phylum Cnidaria?
Cnidocytes
The phylum name "cnidaria" is suggestive of the unique feature it exhibits: the specialised defensive venom cells in them, called cnidocytes. Pinacocytes and choanocytes are cells found in sponges. Gemmules are internal buds found in sponges and are involved in asexual reproduction. It is an asexually reproduced mass of cells, that is capable of developing into a new organism, i.e., an adult sponge.