Nerve net Nerve net A nerve net consists of interconnected neurons lacking a brain or any form of cephalization. While organisms with bilateral body symmetry are normally associated with a central nervous system, organisms with radial symmetry are associated with nerve nets. Nerve nets can be found in members of the Cnidaria, Ctenophora, and Echinodermata phyla, all of which are found in marine environments. Nerve nets can provide animals with the ability to sense objects through the use of the sensory neurons within the nerve net. The nerve net is the simplest form of a nervous system found in multicellular organisms. Unlike
Bacterial phyla prevents it to be validated, such as where the only evidence is DNA sequence data, even if the whole genome has been sequenced. When the species are members of a whole phylum it is called a candidate division (or candidate phylum) and in 2003 there were 26 candidate phyla out of 52. A candidate phylum was defined by Hugenholtz and Pace in 1998, as a set of 16S ribosomal RNA sequences with less than 85% similarity to already-described phyla. More recently an even lower threshold of 75% was proposed. Three candidate phyla were known before 1998, prior to the 85%