File:Medusae of the world (1910) (14595287609).jpg

Identifier: medusaeofworld02mayo (find matches)
Title: Medusae of the world
Year: 1910 (1910s)
Authors: Mayor, Alfred Goldsborough, 1868-1922 Mayer, Alfred Goldsborough, 1868-1922
Subjects: Jellyfishes Cnidaria
Publisher: Washington, D.C., Carnegie institution of Washington
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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arrow end 298 MEDUSA OF THE WORLD. of the pear-shaped planula. This narrow end afterwards becomes invaginated; the invag-inated cells are, however, ectodermal, and have nothing to do with the gastrula cavity, butthey form the cement gland which soon serves to attach the larva. One lip of this orifice ofinvagination grows faster than the other, so that the cavity is soon pushed to one side andthe larva becomes bilateral. When the larva attaches itself this invaginated ectoderm is pro-truded and pours out its cement. The planula then elongates and forms a layer of perisarcwhich fastens it throughout its entire length. It thus becomes a hydrorhiza, not a hydranth.The first hydranth buds out at right angles to the length of the hydrorhiza at the end oppositeto the cement gland. As soon as the first hydranth has acquired mouth and tentacles anotherbuds out close to the base of the first and so on. The planula, therefore, persists as a root(hydrorhiza) and produces the hydranths by budding.
Text Appearing After Image:
Fig. 161.—Larva of Eutima mira, after Brooks, in Mem. Boston Soc. Nat. Hist., vol. 3. The young hydranth has a tentacular basal web and 5 large alternating with 5 smallertentacles; io in all. The body of the hydranth is elongated and cylindrical, and is not coveredby the perisarc which invests the unannulated stem. The hydroid is a Campanopsis, verysimilar to that trom which Claus, 1881, reared Eutima (Octorchis) gegenhauri. Eutima cuculata Brooks. Eutima cuciihita, Brooks, 1883, Studies Johns Hopkins Univ. Biol. Lab., vol. 2, p. 140. Bell about 8 mm. in diameter and quite flat, being about 4 times as wide as high. Thegelatinous substance is quite thick in the center, so that the cavity of the bell is very shallowand forms less than halt ot the total height of the bell. The gelatinous substance diminishesgradually in thickness from the center of the margin, where it forms a thin edge. 4 slendertentacles, which are 3 or 4 times as long as bell-diameter. The basal bulbs of these tenta

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