. Elements of zoölogy. Zoology. Fig. 14.—Lasso-cells of Hydra. 1. Arm of Hydra, containing cells. 2. Cell magnified. 3. Cell after bursting open. position ; more marvelous yet, if when so treated it is spit- ted with a pin or needle so that it can not turn, it will eat and reproduce its kind as if nothing had occurred. Some are solitary, while others live in colonies. They repro- duce by budding (Fig. 13, b, b) and by eggs. Lime-secreting Hydroids {Millepord).—Some of the Hydroids secrete lime. They resemble true corals in appearance, and were long considered as such. Under the microscope, it
. Elements of zoölogy. Zoology. Fig. 14.—Lasso-cells of Hydra. 1. Arm of Hydra, containing cells. 2. Cell magnified. 3. Cell after bursting open. position ; more marvelous yet, if when so treated it is spit- ted with a pin or needle so that it can not turn, it will eat and reproduce its kind as if nothing had occurred. Some are solitary, while others live in colonies. They repro- duce by budding (Fig. 13, b, b) and by eggs. Lime-secreting Hydroids {Millepord).—Some of the Hydroids secrete lime. They resemble true corals in appearance, and were long considered as such. Under the microscope, it will be seen that the lime secreted is tunneled by numerous canals which in life are filled by the animal. The polyps are of two kinds, and, in a millepore found at Tahiti, they are in groups, the largest being stout polyps, with four tentacles, a stomach, and mouth ; but the polyps about it, rising from the smaller pores, have no mouth or stomach, but many tentacles, whose duty is to capture food for the short, thick-set polyp between them. Some of the Hydroids, instead of bearing young like them- selves, produce perfect jelly-fishes {Medusoe) ; such is the Campanularia (Fig. 15), that throws off, by budding, a free jelly-fish (3), that in turn produces eggs that become, not jelly-fishes, but fixed Hydroids (1). This is called alternate generation. The free-swimming young are often brilliant- ly luminous, presenting a wondrous appearance on dark 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 Holder, Charles Frederick, 1851-1915; Holder, Joseph Bassett, 1824-1888, joint author. New York : D. Appleton and company
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
