the distribution of these neurons suggest 3 novel aspects of segmentation in the leech nervous system : ( 1 ) neurons are assigned to even-numbered ganglia through a mechanism which effectively counts through the leech segmental body plan by units of 2 , ( 2 ) neurons are assigned to ganglia 7 and 14 through a mechanism which effectively counts in units of 7 and ( 3 ) neurons are assigned to the 2nd and 4 fused head ganglia and to the 2nd of 21 unfused midbody ganglia through a mechanism which effectively counts units from the origin of these 2 ganglionic series .
C0027763
nervous system
C0270724
plan