. Outlines of zoology. Zoology. AMCEBA—GREGARINA. 87 have an excretory function, and serve to get rid of the finer waste products. Life History.—In favourable nutritive conditions the Amoeba grows. At the hmit of growth it reproduces by dividing into two. In disadvantageous conditions, such as drought, it may become globular, and secreting a cell wall or cyst, lie dormant for a time. With the return of favourable conditions it revives, and, bursting from the cyst with renewed energy, begins anew the cell cycle. The conjuga- tion of two Amcebffi has been observed, and it is said that. Fk;. 16.—
. Outlines of zoology. Zoology. AMCEBA—GREGARINA. 87 have an excretory function, and serve to get rid of the finer waste products. Life History.—In favourable nutritive conditions the Amoeba grows. At the hmit of growth it reproduces by dividing into two. In disadvantageous conditions, such as drought, it may become globular, and secreting a cell wall or cyst, lie dormant for a time. With the return of favourable conditions it revives, and, bursting from the cyst with renewed energy, begins anew the cell cycle. The conjuga- tion of two Amcebffi has been observed, and it is said that. Fk;. 16.—Life history of Amreba. 1. 7t. Nucleus, contractile vacuole. 2. Division into two 3. 4. Escape of amoeba from its cyst. spore formation occasionally occurs; of these processes, however, little is certainly known. Second Type— Gregariiia, a type of those Gregarinida or Sporozoa in which the cell is divided into two regions by a partition. Description.—Various species occur in the intestine of the lobster, cockroach, and other Arthropods. When young they are intracellular parasites, but later they become free in the gut. They feed by absorbing diffusible food stuffs, such as peptones and carbohydrates, from their hosts, and store up glycogen within themselves. The maximum size is about one-tenth of an inch. There is a firm cuticle of " proto- elastin," which grows inwards so as to divide the cell into a larger nucleated posterior region and a smaller anterior region, and also, in the young stage, forms a small anterior cap. The. 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; Newbigin, Marion I. (Marion Isabel), 1869-1934; Smith, Preserved, 1880-1941. fmo. New York, D. Appleton & Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
