Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 Cb so that the ciliated embryo still enclosed in the egg membranes repre- sents a small colony of two individuals. In the marine chilostomatous Bryozoa the fertilized egg passes into the ovicell, which consists of a helmet-shaped capsule and a vesicular operculum. Here the egg segments and develops into an embryo, which passes out as a ciliated larva, and swims about freely in the sea. The irregularly globular larva possesses a ring of cilia (fig. 550, a, b, c). After some time the larva
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 Cb so that the ciliated embryo still enclosed in the egg membranes repre- sents a small colony of two individuals. In the marine chilostomatous Bryozoa the fertilized egg passes into the ovicell, which consists of a helmet-shaped capsule and a vesicular operculum. Here the egg segments and develops into an embryo, which passes out as a ciliated larva, and swims about freely in the sea. The irregularly globular larva possesses a ring of cilia (fig. 550, a, b, c). After some time the larva attaches itself and develops the tentacular crown. The primary zooeciuni soon produces new zooecia by budding ; avicularia are developed, and final- ly, but not until after the death of the old- er zooecia, root fila- ments. In the Endoprocta the egg develops in a brood-pouch placed on the oral side of the animal. The segmentation is complete, and leads to the formation of a blasto- sphere ; the endoderm arises by invagina- tion, and gives rise to the lining of the midgut ; the oesophagus and rectum being formed from the ectoderm t'fig. 551). The mesoderm arises from two cells. The larvse of the Endoprocta possess an alimentary J canal bent into the form of a horse-shoe, and a cilkted coikr which is prot™ded at the front end; further, they contain a bud (fig. 551 e, Kn}, as the first rudiment of a second individual, and a cement gland at the hind end (Dr). Other larval forms, which are apparently of a very different 'structure, are reducible to the same type — , Cyphonautes (fig. 500, c), a larva which is found in all seas, and is, according to Schneider, the larva of Membranipora pilosa. After the winter the contents of the statoblasts give rise to simple, non-ciliated animals, which possess, when they are hatched, all the parts of the adult animal, at once become attached, and produce new colonies by budding. (after Barrois). b, Larva of Le- in-<ii, a (after Ba
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