Whether the two most popular species in biology labs—the roundworm Caenorhabditis elegans, with its 302 nerve cells, and the fruit fly Drosophila melanogaster, with its 100,000 neurons—have any phenomenal states is difficult to ascertain at the moment. Without a sound understanding of the neuronal architecture necessary to support consciousness, we cannot know whether there is a Rubicon in the animal kingdom that separates sentient creatures from those that do not feel anything.
