The Indian flying-squirrel (P. oral) leaps with its parachute extended from the higher branches of a tree, and descends first directly and then more and more obliquely, until the flight, gradually becoming slower, assumes a horizontal direction, and finally terminates in an ascent to the branch or trunk of the tree to which it was directed.
The nematocysts of the ectoderm may be grouped to form batteries on the tentacles, umbrellar margin and oral lappets.
Mechnikov considered the plate thus formed at the base of the polyp as equivalent to the umbrella, and the body of the polyp as equivalent to the manubrium, of the medusa; on this view the marginal tentacles almost invariably present in medusae are new formations, and the tentacles of the polyp are represented in the medusa by the oral arms which may occur round the mouth, and which sometimes, e.g.
Hydranth more shortened, daisy-like in form, with two whorls of tentacles, oral and aboral.
The proboscis bears at its extremity a circlet of smaller oral tentacles.