. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 244 RICHARD A. CLONEY NV. MC FIGURE 1. Amaroucium constellatum; transverse section of the larval tail. The tail is covered by two layers of tunic (T). The outer layer forms the dorsal and ventral fins. The basement membrane of the thin epidermis (E) lies in close contact with 8 rows of muscle cells (MC). Myrofibrils (my) lie in the periphery of each cell. They are underlain by a thick layer of mitochondria (mt). The muscle cells attach to a fibrous sheath of the notochord. Notochordal cells (NC) form a squamous epithelium be
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 244 RICHARD A. CLONEY NV. MC FIGURE 1. Amaroucium constellatum; transverse section of the larval tail. The tail is covered by two layers of tunic (T). The outer layer forms the dorsal and ventral fins. The basement membrane of the thin epidermis (E) lies in close contact with 8 rows of muscle cells (MC). Myrofibrils (my) lie in the periphery of each cell. They are underlain by a thick layer of mitochondria (mt). The muscle cells attach to a fibrous sheath of the notochord. Notochordal cells (NC) form a squamous epithelium beneath the sheath. The axis or lumen (1 ) of the notochord is filled with a clear matrix. The nerve cord (NV) is visible on the right. One-micron Epon section; Richardson's stain. small gaps where adjacent muscle cells lie in close contact. Contrary to the opinion of Grave (1921), Scott (1946) and Berrill (1947), the myofibrils termi- nate near the sarcolemma at the ends of each cell (Jackson, 1958; Cloney, un- published results). A dense layer of mitochondria is located beneath the myofibrils. The nucleus is located near the center of each cell and is surrounded by relatively clear cytoplasm. Lead acetate staining of ultrathin sections suggests the presence of glycogen in these areas. Large, irregular, dense bodies are often found in the cytoplasm of the muscle cells. In electron micrographs these bodies can be seen to contain myelinic figures. The band of muscle cells on the right side of the tail is often shifted slightly with respect to the left band of muscle, giving the tail an asymmetric appearance in section (Fig. 1 ). Notochord. The notochord forms the axis of the tail. In transverse sections the notochord appears elongate in the dorsal-ventral axis and somewhat irregular in shape. In electron micrographs, it is seen to be surrounded by an acellular filamentous sheath. The cells of the notochord are arranged in an epithelium and are attached to the inside of the notocho
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
