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During later stages of development, the neuroectoderm proliferates extensively. The anterior part of the head has newly formed neuron precursor cells that occupy most of the volume. The antenna attached on the worm’s head form the dorsolateral side of the anterior somite. However, antennas do not have its own neuroectoderm and onset of its formation. Neurons, instead migrate out to the appendage form the nearby region of the developing brain. The tract is formed and positioned horizontally in the brain, in line with the antennal commissure. Segments associated with the onychophoran eye and antenna are not homologous with segments carrying equivalent structures. There is evidence to prove that there is a terminal mouth on this worm.



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