A free-living ciliate species called Stentor roeseli, which lacks a central nervous system, is capable of decision making, according to a study published in the journal Current Biology. Stentor roeseli is colorless, trumpet shaped, and visible to the naked eye. Image credit: Protist Image Database. In 1906, American biologist Herbert Spencer Jennings reported that Stentor roeseli exhibited complex behavior. In response to an irritating stimulus, this...
