ABSTRACT
Serial sections of the rabbit embryos measuring 4-14 mm. were carefully studied to compare the developing eye with 36 somites chick embryos and 10-15 mm. pig embryos. The eyes of the 4-5 mm. rabbit embryos were at an earlier stage than those of the 36 somites chick embryos, but at about the same stage as the fifth-week human embryos. At this stage, the optic cups had already formed but some of the lenses had incompleted double fusion. The eye of the 12-14 mm. rabbit embryos were somewhat identical to the 15 mm. pig embryos and can be compared to the sixth week human embryos. At this stage the optic cups were divided into the outer pigment and inner nervous layers; the lens was characterized by a thinner anterior lens epithelium and the longer posterior lens fiber. The mesenchyme surrounding the optic cups of this stage showed a slight condensation to from the vascular and fibrous coats of the eyeball. The rabbit embryos of 4-14 mm. were more suitable for use as laboratory models in studying eye development than of the pig embryos since the latter were no longer available for slide preparation.