. The elements of experimental embryology. Embryology, Experimental; Embryology. 484 APPENDIX have the complete failure of the nervous system to differentiate in the ectodermal portion. The only difference observable between presumptive epidermis and presumptive neural plate is that the latter shows an autonomous tendency to elongation in the direction of the egg's major axis. We shall later return to the absence of ectodermal differentiations. In marked contrast with this incapacity of the ectoderm is the capacity of the endo-mesoderm for self-differentiation. We have in. ^^^ Fig. 216 Transve
. The elements of experimental embryology. Embryology, Experimental; Embryology. 484 APPENDIX have the complete failure of the nervous system to differentiate in the ectodermal portion. The only difference observable between presumptive epidermis and presumptive neural plate is that the latter shows an autonomous tendency to elongation in the direction of the egg's major axis. We shall later return to the absence of ectodermal differentiations. In marked contrast with this incapacity of the ectoderm is the capacity of the endo-mesoderm for self-differentiation. We have in. ^^^ Fig. 216 Transverse section through trunk-region of exogastrulated endo-mesoderm, axolotl. Note superficial endoderm surrounding notochord, myotomes, con- nective tissue, and (below on the right) heart. (From Holtfreter, Arch. Entwmech. cxxix, 1933.) the first place typical notochord. Then the mesoderm produces the following derivatives: in the anterior region, head-musculature, mesenchyme and cartilage; in the trunk-region, somitic mesoderm, pro- and meso-nephric tubules with coelomic funnels and asso- ciated with gonads, smooth gut-musculature and (empty) hearts capable of rhythmical contraction, empty endothelial sacs, masses of blood-cells, coelomic spaces, and connective tissue. The endoderm shows equal powers of self-differentiation, and gives rise to buccal cavity, pharynx with endodermal portion of the gill-clefts (the visible apertures on the surface of the exo-embryo of course corresponding to the normal internal apertures leading out of the. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Huxley, Julian, 1887-1975; De Beer, Gavin, Sir, 1899-1972. New York [Hafner Pub. Co. ]
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Keywords: ., bookcentury1900, bookcollectionbiodiversi, booksubjectembryology
