Beginners' zoology . FlG. 43.— A JELLVKIbH. ance changes entirely and instead of being hydra-hke, itbecomes the large and complex creature called jellyfish(Fig. 43). Butthe egg of theJellyfish pro-duces a smallhydra-like ajii-wrt/which givesrise by buddingto a hydroid,and the cycle iscomplete. The bud (or -reproductivehydranth) ofthe hydroid Fig. 44. —a jellyfish (medusa).. POLYPS {CUPLIKE ANIMALS) 31 does not produce a hydroid, but a jellyfish; the Qgg of thejellyfish does not produce a jellyfish, but a hydroid. This iscalled by zoologists, alternation of generations. A completeindividual is
Beginners' zoology . FlG. 43.— A JELLVKIbH. ance changes entirely and instead of being hydra-hke, itbecomes the large and complex creature called jellyfish(Fig. 43). Butthe egg of theJellyfish pro-duces a smallhydra-like ajii-wrt/which givesrise by buddingto a hydroid,and the cycle iscomplete. The bud (or -reproductivehydranth) ofthe hydroid Fig. 44. —a jellyfish (medusa).. POLYPS {CUPLIKE ANIMALS) 31 does not produce a hydroid, but a jellyfish; the Qgg of thejellyfish does not produce a jellyfish, but a hydroid. This iscalled by zoologists, alternation of generations. A completeindividual is the life from the germination of one Qgg tothe production of another. So that an individual con-sists of a hydroid colony fixed in one place together withall the jellyfish produced from its buds, which maynow be floating miles away from it in the ocean. Bathersin the surf are sometimes touched and stung by the long,streamer-like tentacles of the jellyfish. These, like thetentacles of the hydra, havenettUng cells (Fig. 41). The umbrella-shaped freeswimming jellyfish is called amedusa (Fig. 44). Coral Polyps. — Some of thesalt water relatives of the hydraproduce buds which remain attached to the parent without, ^^^ ^r^LYPs (tenta-however, becoming different cies, a multiple of six\. Notice , ^, ^ . hypostome. from the parent m any way. The coral polyps and cora
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectzoology, bookyear1921
