Medusae of the world . r, onthe other hand, is thin, flexible, and contractile. When expanded the lappets are abouttwo-thirds as long as the bell-radius and their free, lower margins are evenly rounded. Thereare 4 to 8 sensory-clubs on each lappet. Each club arises by a very narrow stalk from a bristle-bearing pad on the bell-margin. The club contains at its distal end a single, red-colored,crystalline concretion of entodermal origin. A thick, linear otoporpa arises from the basalpad of each sensory-club and extends upward for a short distance over the exumbrella sideof the lappet. The velum i
Medusae of the world . r, onthe other hand, is thin, flexible, and contractile. When expanded the lappets are abouttwo-thirds as long as the bell-radius and their free, lower margins are evenly rounded. Thereare 4 to 8 sensory-clubs on each lappet. Each club arises by a very narrow stalk from a bristle-bearing pad on the bell-margin. The club contains at its distal end a single, red-colored,crystalline concretion of entodermal origin. A thick, linear otoporpa arises from the basalpad of each sensory-club and extends upward for a short distance over the exumbrella sideof the lappet. The velum is well developed and provided with powerful, circular muscles. The tentacles, and consequently the lappets, are remarkably variable in number, rangingfrom 7 to 16. There are usually 9 or more tentacles and lappets, but the actual number is soinconstant that there is no well-defined mean. Thus, among 36 medusae studied by me atNaples during the winter of I907-1908, 1 had 7 tentacles, none had 8, 7 had 9, 5 had 10, 6 had. Fig. 320.—Cunina prolifera. Drawn by the author, from sections, at Naples Zoological Station. Ectodermal nuclei areshown as black dots while the entodermal nuclei are represented as circles. A, radial section through medusa inradius of sense-club; m, medusae of first sexual generation floating in stomach-cavity of parent; o, mouth of youngmedusa; or, sensory-club of the parent medusa; otp, otoporpa; re, marginal ring-canal; v, velum. B, mediansection of one of the medusae found in stomach-cavity of parent. This medusa is developing an aboral medusa-bud, o, mouth; st, stomach; t, tentacle. 11, 3 had 12, 5 had 13, 5 had 14, 1 had 15, 3 had 16. The tentacles taper gradually to theirtips, are quite flexible, but not very contractile. They range in length from two-thirds to aslong as the bell-radius. Their number does not increase with age in the free-swimmingmedusa, for large specimens often have a small number and young medusae a larger number oftentacles. The ru
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectcnidari, bookyear1910
