Which organelle is present in a prokaryotic organism, but in a primitive form?

The major differences between Prokaryotic and Eukaryotic cells are that prokaryotes do not have a nucleus as a distinct organelle and rarely have any membrane bound organelles [mitochondria, chloroplasts, endoplasmic reticulum, golgi apparatus, a cytoskeleton of microtubules and microfilaments] (the only exception may

C. Cnidaria, a jellyfish sends shocking jolts through its catch when tangled in the tentacles