Читать книгу Jelly-Fish, Star-Fish, and Sea-Urchins: Being a Research on Primitive Nervous Systems - George John Romanes - Страница 10

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Coming now to the covered-eyed Medusæ, I find that the concentration of the locomotor centres of the margin into the marginal bodies, or lithocysts, is still more decided than it is in the case of Sarsia. Taking Aurelia aurita as a type of the group, I cannot say that, either by excising the lithocysts alone or by leaving the lithocysts in situ and excising all the rest of the marginal tissue, I have ever detected the slightest indications of locomotor centres being present in any part of the margin of the umbrella other than the eight lithocysts; so that all the remarks previously made upon this species, while we were dealing with the effects of excising the entire margin of umbrellas, are equally applicable to the experiment we are now considering, viz. that of excising the lithocysts alone. In other words, but for the sake of symmetry, I might as well have stated at the first that in the case of the covered-eyed Medusæ all the remarkable paralyzing effects which are obtained by excising the entire margin of an umbrella are obtained in exactly the same degree by excising the eight lithocysts alone; the intermediate marginal tissue, in the case of these Medusæ, is totally destitute of locomotor centres.