. Principles of modern biology. Biology. PROTONEURON CELL TYPES - CLOSELY ASSOCIATED SENSORY CELL Fig. 32-8. Hydra. Diagram of cellular structure. Note the different types of cells and the absence of clearly organized tissues and organs. 1, nematoblast; 2, interstitial cell; 3, ecto- dermal cell; 4, mesoglea; 5, endodermal cell; 6, gland recognizable and there are no other well- developed organs. Sometimes the body is covered by a horny, but delicately transpar- ent envelope as in the case of Obelia (Fig. 32-9). Also many Coelenterata, especially the coral animals, secrete supporting st
. Principles of modern biology. Biology. PROTONEURON CELL TYPES - CLOSELY ASSOCIATED SENSORY CELL Fig. 32-8. Hydra. Diagram of cellular structure. Note the different types of cells and the absence of clearly organized tissues and organs. 1, nematoblast; 2, interstitial cell; 3, ecto- dermal cell; 4, mesoglea; 5, endodermal cell; 6, gland recognizable and there are no other well- developed organs. Sometimes the body is covered by a horny, but delicately transpar- ent envelope as in the case of Obelia (Fig. 32-9). Also many Coelenterata, especially the coral animals, secrete supporting structures at the basal (attached) end of the body. Usu- ally these are composed of calcareous mate- rial, but sometimes they have a protein com- position. (9) All Coelenterata are aquatic, chiefly marine. Classes of the Phylum Coelenterata. Three distinct classes have been evolved among coelenterate animals. These may be listed as follows: Class 1. The Hydrozoa (Hydra, Obelia, and Related Forms). At some stage in the life cycle, typical Hydrozoa tend to resemble Hydra. Many are colonial, however. Also many dis- play an alternation of generations, which is a phenomenon cpiite rare in the animal king- dom. In the case of Obelia (Fig. 32-9), for example, the asexual hydroid generation is represented by the colonial form of the or- ganism, in which the individual members of the colony display a hydralike form; whereas the sexual medusoid generation takes 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 Marsland, Douglas, 1899-. New York, Holt, Rinehart and Winston
Size: 1553px × 1609px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionbiodiversity, booksubjectbiology
