. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. the retraction of the epidermis alone, while the NMN-complex actually pushes away from the trunk as if released from tension as soon as it detaches from the epidermis. The mechanism of epidermal contraction is of general biological interest. The following is quoted from Hoffmann-Berling (1960, p. 346). "All in all, it may be stated that systematic comparisons have not yet uncovered anv dissimilarity which would indicate a fundamental difference between the con- , * traction of a muscle and the contraction of an undiffer
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. the retraction of the epidermis alone, while the NMN-complex actually pushes away from the trunk as if released from tension as soon as it detaches from the epidermis. The mechanism of epidermal contraction is of general biological interest. The following is quoted from Hoffmann-Berling (1960, p. 346). "All in all, it may be stated that systematic comparisons have not yet uncovered anv dissimilarity which would indicate a fundamental difference between the con- , * traction of a muscle and the contraction of an undifferentiated cell. The differ- ences are only quantitative. The mechanism of muscle contraction is already present in the final form at the developmental stage of the single cell organism prior to the start of organ formation and tissue specialization. It is older than muscle ; Unpublished electron micrographs revealed filaments in the epidermis of Amaroucium larvae, but filaments are commonly found in epidermal cells, as well as many other epithelial cells in which active contraction is at least not obvious. Contractility may be one of the fundamental properties of all cells but in the case of tail resorption, some cells contract in a specific and predictable way while other cells of the tail do not perceptibly contract. These epithelial cells may be suitable subjects for further investigations of this long-standing problem. SUMMARY 1. Tail resorption in Ainaroitchiui is a rapid morphogenetic process. It is usually complete within only 6 minutes. 2. The initiation of tail resorption is signaled by a rapid separation of the epi- FIGURES 7-10. Amaroucium constellatum; sequence of events following the excision of the distal one-third of the tail; living specimen. Immediately after the beginning of tail resorption the tail was excised and photographed. The epidermis began to shorten by contracting over the surface of the underlying NMN-complex. Within two minutes the epide
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
