. The Cambridge natural history. Zoology. xin ALCYONARIAâDEVELOPMENTâCLASSIFICATION 341 â Ec. It is not known for certain when the fertilisation of the ova is effected, but in Alcyoniiom digitatum, and in the majority of the Alcyonarians, it probably takes place after the discharge of the ova from the zooids. A few forms are, however, certainly viviparous, the larvae of Gorgonia capensis being retained within the coelenteric cavity of the parent zooid until they have grown to a considerable size. The other viviparous Alcyonarians are Coral- Hum nobile (de Lacaze Duthiers), the " Clavulair
. The Cambridge natural history. Zoology. xin ALCYONARIAâDEVELOPMENTâCLASSIFICATION 341 â Ec. It is not known for certain when the fertilisation of the ova is effected, but in Alcyoniiom digitatum, and in the majority of the Alcyonarians, it probably takes place after the discharge of the ova from the zooids. A few forms are, however, certainly viviparous, the larvae of Gorgonia capensis being retained within the coelenteric cavity of the parent zooid until they have grown to a considerable size. The other viviparous Alcyonarians are Coral- Hum nobile (de Lacaze Duthiers), the " Clavulaires petricoles," and Sympodium coralloides (Marion and Kowalevsky), and three species of Nephthya found at depths of 269 to 761 fathoms (Koran and Danielssen). The general features of the development are very similar in all Alcyonarians that have been investigated. The egg contains a considerable amount of yolk, and undergoes a modified form of seg- mentation. The free-swimming larva is called a " ; It consists of an outer layer of clear ciliated ectoderm cells, surrounding a solid Fir. 150.âCiliated "planula" larva endodermic Plasmodium containing of Aicyoniwm digitatum. Ec, ^ . *? Ectoderm; End, endoderm. the yolk. As the yolk is consumed a cavity appears in the endoderm, and the larva is then called a "planula" (Fig. 150). The mouth is subsequently formed by an invagination of the ectoderm at the anterior pole. The development of the mesenteries has not yet been fully described. Classification.âThe sub-class Alcyonaria may conveniently be classified as follows:â. Grade A. Pkotalcyonacea. Grade B. Synalcyonacea. Order 1. Stolonifeea. Order 2. Coenothecalia. Order 3. Alcyonacea. Order 4. Gorgonacea. Order 5. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the orig
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
