Memoirs: On the Developement of the Optic Nerve of Vertebrates, and the Choroidal Fissure of Embryonic Life

Abstract

1. The optic stalk takes no part in the formation of the nervous parts of the organ of sight. 2. The optic stalk becomes broken down and the cells composing it separated from one another, partly by the mechanical stretching due to the growth of the optic nerve, partly by the growth in between the several cells of the nerve-fibres. 3. The optic nerve is developed independently of the optic stalk, the nerve-fibres lying along the posterior border of the stalk, and at first entirely outside it; but on the breaking down of the stalk some of the nerve-fibres grow in between the cells. 4. The great majority of fibres forming the optic nerve arise as outgrowths from nerve-cells in the retina, and grow towards and into the brain. 5. According to Cajal's researches certain fibres also exist which would seem to grow from the central nervous system to the retina, but these I have not been able to find. 6. The nerve-fibres pass over the ventral edge of the optic cup, and thereby cause the formation of the choroidal fissure. 7. The choroidal fissure of the embyro represents a condition in the evolution of the eye which was persistent in the adult prior to the formation of a lens. It has only secondarily been made use of as a means of ingress for the mesoblastic tissues.