Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] 198 ZOOLOGY or by the production of new animals by means of eggs and sperms, sexually. The bud appears on the body as a little knob, some- times more than one coming out on the same hydra. At first the bud is part of the parent animal, the body cavity extending into it. After a short time (usually a few days) the young hydra separates from the old one and begins life anew in another place. This is asexual reproduction. The hydra als
Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] 198 ZOOLOGY or by the production of new animals by means of eggs and sperms, sexually. The bud appears on the body as a little knob, some- times more than one coming out on the same hydra. At first the bud is part of the parent animal, the body cavity extending into it. After a short time (usually a few days) the young hydra separates from the old one and begins life anew in another place. This is asexual reproduction. The hydra also reproduces by eggs and sperms. These sperms are collected in little groups which usually appear near the free end of the animal, the egg cells developing near the base of the same hydra. Both eggs and sperms grow from the middle layer of the animal. The sperms when ripe are set free in the water, one of them unites with an egg, which is usually still attached to the body of the hydra, and development begins which results in the growth of a new hydra in a new locality. Medusa. — The coelenterate animals are a very large group and contain many other animals than the hydra. All of this group of animals are found in the water, by far the greatest number of forms living in the ocean. Among the most interesting of all the coelenterates inhabiting the salt water are the jelly fishes or medusae. For the study of the Me- dusae^ use Gonionemus pre- served in formol. Why should you call it a 'jellyfish'? Notice the shape of the animal, some- what like an umbrella with a short handle. What do you find hanging from the edge of the umbrella? The tentacles of the medusa are provided with stinging cells. Find and describe the mouth at the end of the handle of the umbrella (manubrium). ( A little car- mine or methylene blue dissolved in water may be forced into the mouth of the specimen with a small medicine dropper. This will show clearly the di- gestive cavity and its canals). Notice
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