Journal of morphology . t carefulstudy of many specimens indicates that in all probability thisis not the case. Any line of pigment granules communicatesonly with the body of one cell and does not continue overto that from a neighboring cell. This view is materiallystrengthened by the observations of Ramon y CajaP upon the 1 Ramon y Cajal, Anatom. Anz., 1889. No. 2.] HISTOGENESIS OF THE RETINA. 421 adult retina. By means of Golgis method he succeeded inoutlining large cells extending from the rods and cones tothe nerve fibers of the retina. There are no anastomosesbetween the prolongations and
Journal of morphology . t carefulstudy of many specimens indicates that in all probability thisis not the case. Any line of pigment granules communicatesonly with the body of one cell and does not continue overto that from a neighboring cell. This view is materiallystrengthened by the observations of Ramon y CajaP upon the 1 Ramon y Cajal, Anatom. Anz., 1889. No. 2.] HISTOGENESIS OF THE RETINA. 421 adult retina. By means of Golgis method he succeeded inoutlining large cells extending from the rods and cones tothe nerve fibers of the retina. There are no anastomosesbetween the prolongations and in general their outline corre-sponds with my Figs. 4, 5 and 6. In every respect theycorrespond with the Miillers fibers of the inner nuclear layerand I shall speak of them as such. A day later the nuclei have all moved to the basal end ofthe cells, leaving on the free side of the retina a zone com-posed wholly of the prolongations of the spongioblasts. Thisfree zone or peripheral veil of His {Randschlcier) is not only. Fig. 6. — Section through the eye of Amblystoma (7 mm. long) twelve daysbefore hatching. X 133 times. G, germinating cell; S, spongioblast. present in the retinas of all classes of vertebrates but extendsthroughout the central nervous system, and is in all cases onthe basal side of the ectoderm. Without demonstrating thepoint absolutely the embryological evidence is that the spongi-oblasts throughout the nervous system are much the same —forming Mullers fibres and the retina, and Deiters cells in thebrain and spinal cord. And as the evidence is graduallyaccumulating we must admit that the prolongations of thespongioblasts do not communicate directly but only come in. 42: MALL. [Vol. VIII. apposition, so that the same principle applies to them as to thenerve-cells, or to cells in general. Fig. 5 is a stage two clays in advance of Fig. 4. The fatglobules in this case show how the peripheral end of the cell isbreaking up into its prolongations. The process is
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