...In particular, in annelids and arthropods, the segments are called ring segments because they form a ring. If we define a segment as "a part of the body with the same structure that has the same organs and is repeated in the front-to-back direction," then the strobila (transverse divisions) that occur during reproduction in tapeworms and certain coelenterates are also made up of many segments of the same type. However, the origin of these segments is of a completely different nature, and the latter segments can be seen as insect bodies that reproduce asexually in the vertical direction, but do not separate from the mother body and remain as parts of the original individual forever, with the front ones losing their tails and the rear ones losing their heads at the connection point. ... *Some of the terminology explanations that mention "lateral division" are listed below. Source | Heibonsha World Encyclopedia 2nd Edition | Information |
…ことに環形動物や節足動物ではそれが輪状の環をなしているので環節という。ところで体節をこのように〈同種の器官をそなえて前後の方向に反復する同じ構造の体の一部〉と定義すると,サナダムシやある種の腔腸動物の繁殖時におけるストロビラstrobila(横分体)もまた同型の多くの節からできている。しかしその節の起原はまったく違った性質のもので,いわば後者の分節は縦の方向に無性分殖をした虫体が,母体から離れないでいつまでも元の個体の一部分としてとどまり,その連絡位置で前のものは尾を,後のものは頭を失った姿と見ることができよう。… ※「横分体」について言及している用語解説の一部を掲載しています。 出典|株式会社平凡社世界大百科事典 第2版について | 情報 |
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