Atolla jellyfish
The body of "Atolla wyvillei" is a bell shape and it has several moderately long tentacles along the bell. The bell is around 20–174 mm in diameter. It also has a single long tentacle called a hypertrophied tentacle. This hypertrophied tentacle has several purposes, including aid in predation and aid in reproduction. These jellyfish do not have a digestive system, a respiratory system, a circulatory system or a central nervous system. Not having a central nervous system means that it lacks a brain.
Fish
Fish brains are divided into several regions. At the front are the olfactory lobes, a pair of structures that receive and process signals from the nostrils via the two olfactory nerves. The olfactory lobes are very large in fish that hunt primarily by smell, such as hagfish, sharks, and catfish. Behind the olfactory lobes is the two-lobed telencephalon, the structural equivalent to the cerebrum in higher vertebrates. In fish the telencephalon is concerned mostly with olfaction. Together these structures form the forebrain.