. Outlines of zoology. Zoology. Fig. 154.—Development of Anodonta.—After Gcette. x. Section of blastosphere. , Shell gland : , ciliated disc ; e., beginning of ectodermic invagination. Note mesoderm cells in the cavity. 2. Later stage, in., Mesoderm. 3. Embryonic shell has appeared. 4. Glochidium larva ; note byssus threads, and teeth on shell valves. is slower in dividing. Eventually » hollow ball o- cells or blasto- sphere results (Fig. 154). On the posterior dorsal region a number of large opaque cells form an internally convex plate,—the beginning of the future shell-sac. A pair of
. Outlines of zoology. Zoology. Fig. 154.—Development of Anodonta.—After Gcette. x. Section of blastosphere. , Shell gland : , ciliated disc ; e., beginning of ectodermic invagination. Note mesoderm cells in the cavity. 2. Later stage, in., Mesoderm. 3. Embryonic shell has appeared. 4. Glochidium larva ; note byssus threads, and teeth on shell valves. is slower in dividing. Eventually » hollow ball o- cells or blasto- sphere results (Fig. 154). On the posterior dorsal region a number of large opaque cells form an internally convex plate,—the beginning of the future shell-sac. A pair of large cells are intruded into the central cavity, and begin the mesoderm. On the under surface posteriorly there is a slight protrusion of ciliated cells forming a ciliated disc. In front of this, at an unusually late stage, an invagination establishes the archenteron, and the embryo becomes a gastrula (see Fig. 154). The shell-sac forms an embryonic shell, and many of the mesodeim. 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 Thomson, J. Arthur (John Arthur), 1861-1933. Edinburgh, Glasgow and London, H. Frowde and Hodder & Stoughton
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
