. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. STVLASTERIDAE The Stylasteridae of the North Atlantic. Pliobothrus Pourtales The colonies are branched fan-shaped, often with dichotomonsly divided brandies and branchlets. The gasteropores and dactylopores open irregularly over the surface of the colony and are not collected into cyclic systems. The dactylopores open out on the top of lower or higher tubular projections. The gasteropores are of varying depth, sometimes closed below by one or more tabulae; both the gasteropores and dactylopores sometimes open without distinc
. The Danish Ingolf-Expedition. Scientific expeditions; Arctic Ocean. STVLASTERIDAE The Stylasteridae of the North Atlantic. Pliobothrus Pourtales The colonies are branched fan-shaped, often with dichotomonsly divided brandies and branchlets. The gasteropores and dactylopores open irregularly over the surface of the colony and are not collected into cyclic systems. The dactylopores open out on the top of lower or higher tubular projections. The gasteropores are of varying depth, sometimes closed below by one or more tabulae; both the gasteropores and dactylopores sometimes open without distinct ending into the large, irregular, central longitudinal canals of the colony. The gasteropores and the dactylopores have no styles. With this diagnosis the genus agrees fairly closely with the Pliobothrus of Moseley (1881 p. 94). There are a few changes however which require further mention. Moseley included as a generic character in his diagnosis the absence of tentacles in the gasterozooid, in spite of the fact, that his own investigations indicated that Pliobothrus tubulatus Pourtales has 5—6 tentacles on the gasterozooids. When we remember the great variation to which the number of tentacles is subject in other genera, where they have been studied, this character is of extremely problematic value as generic character. The same applies to the form of the polyps, which more than anything else is dependent on the state of contraction and preservation. So long as we are unable to demonstrate more constant peculiarities in the form of the polyps than hitherto, it has no great value even as specific characteristic. The number of the gonophores in the ampullae must also be referred to the specific characteristics and may even here be of subordinate importance. A close study of Pliobothrus symmetricus shows, that the pores of the zooids vary greatly in length and often stand in open communication with the large central canals which appear irregularly in the branches. This blots
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectscientificexpedition
