Figure 3 Comparison of Primary Chemoreceptor Neurons in Vertebrates, Insects, and Nematodes Diagrams compare primary chemoreceptor neurons in the vertebrate olfactory epithelium (A), an insect olfactory sensillum (B) and the nematode amphid orga... Figure 3. Comparison of Primary Chemoreceptor Neurons in Vertebrates, Insects, and NematodesDiagrams compare primary chemoreceptor neurons in the vertebrate olfactory epithelium (A), an insect olfactory sensillum (B) and the nematode amphid organ (C), drawn to appear the same size. Note that all are small, bipolar neurons that terminate in a ciliary arbor and send their axon without branching to the CNS. From Ache, 1991. Barry W. Ache , Janet M. Young Olfaction: Diverse Species, Conserved Principles Neuron Volume 48, Issue 3 2005 417 - 430 http://dx.doi.org/10.1016/j.neuron.2005.10.022