. Text-book of embryology. Embryology. IV COELENTEEATA 87 (1901), have added nothing of any importance. Wilson worked on the species Renilla reniformis and Leptogorgia virgulata (1883). The eggs are expelled from the parent colonies and fertilized in the sea. The endoderm appears to be formed by proliferation, and all the eight mesenteries appear at once. The arrangement of the muscular thickenings on these mesenteries differs only from that in the Edwardsia stage of Hexactiniae, in the fact that the thickenings of the ventral directives face each other instead of being turned away from each o
. Text-book of embryology. Embryology. IV COELENTEEATA 87 (1901), have added nothing of any importance. Wilson worked on the species Renilla reniformis and Leptogorgia virgulata (1883). The eggs are expelled from the parent colonies and fertilized in the sea. The endoderm appears to be formed by proliferation, and all the eight mesenteries appear at once. The arrangement of the muscular thickenings on these mesenteries differs only from that in the Edwardsia stage of Hexactiniae, in the fact that the thickenings of the ventral directives face each other instead of being turned away from each other. Wilson's observations on the origin of the filaments have already been dealt with. The Alcyonaria differ less in this respect from the Edwardsiae than these differ from the Cereanthidste, and the real ground of their separation from the Zoantharia lies in. the method of forming the skeleton, as will now be made clear. The popular name Sea- Anemone is usually given to those Zoantharia which do not develop a calcareous skeleton, whilst those which do form skeletons are termed Coral- forming Polyps — or briefly. Corals. The development of the skeleton in these was first worked out by Lacaze-Duthiers (1864), but the subject was again taken up and thoroughly examined by von Koch (1897), whose latest investigations deal with the Mediterranean species CaryophyUia cyathus. The first part of the skeleton to appear is the basal plate which is secreted by the pedal disc of the polyp. This basal plate appears as six separate areas of calcareous deposit, one area being situated beneath the space intervening between each pair of mesenteries. They eventually coalesce to form, first a six-rayed star and then a circular disc. In the centre of each of the original areas the process of secretion of calcareous matter continues more actively than else- where and the consequence of this is the formation of six radiating septa'of calcareous matter, each septum being covered by an inwardly pro
Size: 1673px × 1493px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpubli, booksubjectembryology
