n. An embryonic cell:n. One of two large cells or teloblasts which are situated at the posterior end of the body in the annelid embryo and larva and give rise to the ventral nerve-cord of the adult animal.n. One of the cells in the embryonic brain and spinal cord of vertebrates. These cells are said to give rise without division to the ganglion-cells.n. In arthropod embryos, certain ectodermal cells which proliferate inward from the surface to form rows of elements that become the ganglion-cells.