Hydra

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Hydra

a genus of the coelenterate class Hydrozoa. Most species are found in freshwater, and are unusual members of the Hydrozoa in not having an ALTERNATION OF GENERATIONS.
References in periodicals archive ?
When hydras are exposed to toxic substances, they may undergo graded changes in their body structure, which can be used as indicative of the degree of toxicity to be assayed at lethal or sublethal concentrations.
So 10 hydras will become 20 in two days, and in two more days there will be 40
Begin to look for hydras on the brightest sides of the jars.
2 December 2011 - Clean energy technologies holding American Security Resources Corporation (OTCBB:ARSC) announced the completion of the merger between its unit Hydra Fuel Cell Corporation and technology developer iVoice Inc (OTCBB:IVOI), effective 30 November 2011.
Hydra are a particularly good model in which to study nervous system development because they have a few easily observed morphologically and immunochemically defined neuron types.