Abstract
Local vital stains were applied to the prospective head region in the late yolk plug stage of Amblystoma punctatum by Vogt's 1 method. From the records obtained by making camera lucida drawings of the position and extent of the stained areas in the stages following, composite diagrams were constructed showing the arrangement of the parts of the prospective ectoderm involved in the formation of the nose, lens, ear, balancer, gills and stomodaeum. Two of these, Harrison stages 13 (slit blastopore) and 22 (shortly after closure of neural folds), are shown in the figures.
The wheeling about of the head epidermis due to the dorsal convergence of the neural material which lies almost out at the equator of the embryo in the gastrula stage, takes place in Amblystoma punctatum in a manner similar to that observed by Vogt 2 and Goerttler 3 on European salamanders. There is a forward and downward growth of the ectoderm of the head region anteriorly in such a way that the material at the middle of the transverse fold comes to lie just in front of the stomodaeum and ventral to the eye—a shifting of the material nearest the dorsal midline in an anterior and ventral direction while that originally ventral moves caudally and dorsally.
The results obtained for Amblystoma are much less diagrammatic than those Röhlich 4 gives for Triton but the arrangement of the anlagen is essentially the same in both forms. The position of the lens agrees with that given by both Manchot 5 and Röhlich for Triton. In Amblystoma however the nasal ectoderm seems to extend up on the outer side of the neural fold (stage 15) for a short distance and the ear ectoderm not quite to reach the fold. The latter may also be slightly farther anterior in Amblystoma than in Triton.
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