Phoronis sentence example

phoronis
  • The suggestion to place Brachiopods with the Polyzoa, Phoronis, Rhabdopleura and Cephalodiscus, in the Phylum Podaxonia made in Ency.
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  • On the view that the Phylactolaemata are nearly related to Phoronis (see Phoronidea), it is extremely difficult to draw any conclusions with regard to the significance of the facts of development.
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  • If the Phylactolaemata were evolved from the type of structure represented by Phoronis or the Pterobranchia, the Gymnolaen ata should be a further modification of this type, and the comparative study of the embryology of the.two orders would appear to be meaningless.
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  • It seems more natural to draw the conclusion that the resemblances of the Phylactolaemata to Phoronis are devoid of phylogenetic significance.
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  • The conception of the Dipleurula derives its chief weight from the fact that it is comparable to the early larval forms of other primitive coelomate animals, such as Balanoglossus, Phoronis, Chaetognatha, Brachiopoda and Bryozoa.
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  • Such a form as this is roughly represented to-day by the Actinotrocha larva of Phoronis, the importance of which has been brought out by Masterman.
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  • Phoronis is often gregarious, the tubes which it secretes being sometimes intertwined in an inextricable mass.
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  • These associations of individuals can hardly be the result of the metamorphosis of a corresponding number of larvae, but are probably due to a spontaneous fragmentation of the adult animals, each such fragment developing into a complete Phoronis (De Selys-Longchamps).
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  • The eggs of Phoronis are small and usually undergo their early development attached to the tentacles of the adult.
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  • The development of Phoronis was supposed by Caldwell (2) to furnish the explanation of the relations of the surfaces in Brachiopoda, Polyzoa and perhaps the Sipunculoid Gephyrea, in which the ontogenetic evidence is less clear.
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  • There is, however, a considerable amount of resemblance between the lophophore of Phoronis australis, with its spirally twisted ends, and that of a typical Brachiopod; nor do the structural details of the adult Brachiopods forbid the view that they may be related to Phoronis.
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  • The comparative study of the development does not support the hypothesis that the Polyzoa (q.v.) are comparable with Phoronis.
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  • The supposed occurrence of a pair of nephridia in certain Phylactolaemata, in a position corresponding with that of the nephridia of Phoronis, must also be mentioned, although it has been maintained that the "nephridia " of Phylactolaemata are merely ciliated portions of the body-cavity and not indeed nephridia at all.
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  • But a serious objection to the comparison is that the development of Phylactolaemata can be explained by supposing it to be a modification of what occurs in other Polyzoa, while it appears to have no relation whatever to that of Phoronis.
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  • It will be noticed that the lophophore of Phoronis is, on this assumption, a derivative of the collar just as it is in the Pterobranchia.
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  • The epistome of the adult Phoronis cannot well be the proboscis since its cavity is continuous with the lophophoral coelom, and because the praeoral hood of Actinotrocha is entirely lost at the metamorphosis.
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  • It is possible that this consideration will account for the want of an anterior body-cavity in Phoronis.
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  • In spite of the criticisms which have been made on the conclusion that Phoronis is allied to the Pterobranchia, it is thus possible that the view is a sound one, and that the Phoronidea should take their place, with the Enteropneusta and the Pterobranchia, as an order of the Hemichordata.
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  • Their relations to Phoronis are doubtful (see Phoronidea).
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  • Phoronis has long been regarded as a possible ally of Rhabdopleura (see Pterobranchia); and Masterman (to) has attempted to demonstrate the existence in Actinotrocha of most of the structures which occur in the Pterobranchia.
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