Section 14. We May Now Consider the Development of the Different

organs slightly more in detail, though much of this has already been approached. The nervous system, before the closure of the neural groove, has three anterior dilatations, the fore-, mid-, and hind-brains, the first of which gives rise by hollow outgrowths to two pairs of lateral structures, the hemispheres and the optic vesicles. The latter give rise to the retina and optic nerve as described in {Development} Section 40.