. Advanced biology. Biology; Physiology; Reproduction. i?-. Fish seldom show secondary sex characters. The sex organs are the ovaries in the female, and the testes in the male. The ovary produces nu- merous ova, each of which contains a yolk and a nucleus. The testis produces numerous sperms, each of which has a nucleus, a head, and a motile tail. -heocdL, nucleus -tccil. cytoplorsm. river fish spawn in the ocean. So powerful is the urge to spawn in natural spawning grounds, that the salmons will leap falls or artificial barriers in their eftorts to reach quiet water on their way from the deep
. Advanced biology. Biology; Physiology; Reproduction. i?-. Fish seldom show secondary sex characters. The sex organs are the ovaries in the female, and the testes in the male. The ovary produces nu- merous ova, each of which contains a yolk and a nucleus. The testis produces numerous sperms, each of which has a nucleus, a head, and a motile tail. -heocdL, nucleus -tccil. cytoplorsm. river fish spawn in the ocean. So powerful is the urge to spawn in natural spawning grounds, that the salmons will leap falls or artificial barriers in their eftorts to reach quiet water on their way from the deep sea. Many die of exhaustion on their w^ay if they meet too many obstacles. Those that surmount the barriers usu- ally die soon after spawning. Production of eggs. Certain organs of the frog are specialized for the production of gametes. In the female, the two ovaries secrete hundreds of tiny ova. The ovaries may be compared to the ovaries or pistils of flowers which produce egg cells. Ovaries are common to all females in the animal kingdom. The ova of the frog go through a maturation process in which the number of chromosomes is reduced one half. This process results in the production of mature gametes. The mature ova reach the body cavity of the frog and then pass through the tubes called oviducts into the cloaca. They leave the cloaca by means of an open- ing at the posterior end of the female frog's body and pass into the surrounding water. Ova are characterized by their compara-. 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 Wheat, Frank Merrill; Fitzpatrick, Elizabeth T. New York ; Boston [etc. ] : American Book Company
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Keywords: ., bookcentury1900, bookdecade1920, booksubje, booksubjectphysiology
