Axon-guidance by Slit-Roundabout (Robo) signaling at the midline initially guides growth cones to synaptic targets and positions longitudinal axon tracts in discrete bundles on either side of the midline. Following the formation of commissural tracts. Slit is found also in tracts of the commissures and longitudinal connectives. the purpose of which is not clear. https://macorners.shop/product-category/acrylic-photo-film-strip/