. Biology. Biology. 86 ORGANISMS OF TISSUES are sometimes called nematoblasts or cnidoblasts, thus perform functions of offence and defence. Each stinging cell possesses a sensory hair or " trigger," called a cnldocil, at the free end, and a thread-holding capsule, the nematocystj within. The thread is formed from a cell growth which is spirally wound in the capsule, while capsule and its contents are all formed by differentiation of a single nucleated cell of the ectoderm. During growth of the capsule and thread the young nettle cells first lie near the supporting. FIG. 36.—Diagramm
. Biology. Biology. 86 ORGANISMS OF TISSUES are sometimes called nematoblasts or cnidoblasts, thus perform functions of offence and defence. Each stinging cell possesses a sensory hair or " trigger," called a cnldocil, at the free end, and a thread-holding capsule, the nematocystj within. The thread is formed from a cell growth which is spirally wound in the capsule, while capsule and its contents are all formed by differentiation of a single nucleated cell of the ectoderm. During growth of the capsule and thread the young nettle cells first lie near the supporting. FIG. 36.—Diagrammatic figure of the cells from a small portion of the body wall of Hydra mridis; the ectodermal cells with nematocysts below (one with pro- truded thread), and the large vacuolated endoderm cells above. The symbiotic algae are grouped near the supporting lamella at the bases of the endoderm cells. (From Marshall and Hurst.) lamella in the region of the mouth, but they migrate during the period of their formation, and finally come to lie on the sur- face of the ectoderm around the mouth or on the tentacles and body, the cnidocils ultimately projecting slightly beyond the surface of the body in the surrounding medium (Fig. 36). 3. Nerve nerve cells of Hydra and the coelenter- ates represent the special differentiation of cells for the per-. 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 Calkins, Gary N. (Gary Nathan), b. 1869. New York, H. Holt and company
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