Intraocular differentiation of rat egg cylinders

The anterior chamber of the eye is a suitable environment for testing the capacities of embryonic shields of the mouse to differentiate, as has been shown by Grobstein (1951). The development proceeds at a slower rate than usually and no morphogenesis is observed, although many identifiable tissues are found. The differentiation progressively increases as later stages are used. On the other hand, if younger stages, e.g. tubal ova or morulae, are transplanted (Runner, 1947), no histogenesis can be obtained although the germ layers are formed. The purpose of the present study has been to test the capacity of differentiation of two distinctly defined stages of rat embryo: one prior to mesoderm formation and the other with the mesoderm already formed. It is well known (Huber, 1916; Wilson, 1954; Mulnard, 1955) that the onset of mesoderm formation occurs in the rat during the 9th day of gestation, and this has been verified by our own material.