“…The embryonic development of S. officinalis is arbitrarily subdivided into 30 stages based on major morphological changes (Lemaire, 1970). Organogenesis and neurogenesis start at around stage 12 and quickly form the nervous system with all of its components (Figure 1c) including the sensory organs and sensory cells (Baratte & Bonnaud, 2009;Buresi et al, 2014;Darmaillacq, Lesimple, & Dickel, 2008;Imarazene, Andouche, Bassaglia, Lopez, & Bonnaud-Ponticelli, 2017;Shigeno, Kidokoro, Tsuchiya, Segawa, & Yamamoto, 2001a;Shigeno, Tsuchiya, & Segawa, 2001b;Yamamoto, Shimazaki, & Shigeno, 2003), the integrative centers (Aroua, Andouche, Martin, Baratte, & Bonnaud, 2011;Buresi et al, 2014), and the connection of motor fibers to their target organs (Baratte & Bonnaud, 2009) early during organogenesis (Romagny, Darmaillacq, Guibe, Bellanger, & Dickel, 2012) soon after the differentiation of the associated sensory neurons ( Figure 1d). As we aimed to describe the distribution of HAergic neurons, this early sensory system development, in addition to the cephalopod's direct development life history, makes late-stage embryos (stages 27-30) a convenient model for sensory system and CNS observations.…”