焦虑 发表于 2025-3-28 17:35:54

Ecosystem Engineers, Keystone Species,anus. A curious feature of the Nematodes is that the tissues of which their bodies are composed are made up of very few large cells; there are no cilia anywhere, no blood system, and no breathing organs. The eggs are covered by a hard shell. The young Nematode hatches looking very much like an adult

束缚 发表于 2025-3-28 22:24:01

Patrick M. A. James,Marie-Josée Fortin(.) on their bodies which are arranged in groups on each segment; they are used to obtain a hold on the sides of burrows, and they are a very valuable means of identifying a specimen. Worms all have distinct heads and tails though it is sometimes difficult to see which is which, but the mouth is ove

Suppository 发表于 2025-3-29 02:53:17

Heinrich Walter,Siegmar-W. Brecklee the limbs used for locomotion (i.e. walking or swimming). The skin on the surface of the animals contains a particular substance called chitin and is waterproof. Frequently most of the skin tends to be rather hard and brittle, and movement would be difficult were it not that between the segments o

急性 发表于 2025-3-29 06:28:07

Heinrich Walter,Siegmar-W. Breckleciliated, and the cilia make currents which collect the small organisms used as food, and transport them to the mouth. Polyzoa possess a proper gut, which terminates in an anus; ovaries and testes (they are hermaphrodites); and a rudimentary nervous system. The fresh-water polyzoa reproduce asexuall

panorama 发表于 2025-3-29 09:45:01

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BET 发表于 2025-3-29 12:48:58

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figment 发表于 2025-3-29 16:20:21

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acolyte 发表于 2025-3-29 21:09:04

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漂亮才会豪华 发表于 2025-3-30 00:44:48

The True Worms (,),(.) on their bodies which are arranged in groups on each segment; they are used to obtain a hold on the sides of burrows, and they are a very valuable means of identifying a specimen. Worms all have distinct heads and tails though it is sometimes difficult to see which is which, but the mouth is ove

外面 发表于 2025-3-30 06:29:31

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查看完整版本: Titlebook: Animal Life in Fresh Water; A Guide to Fresh-Wat Helen Mellanby Book 1963 Helen Mellanby 1963 evolution.invertebrates.physiology.Model inve