. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. :—caltcczoa. 057 ti) Sub-oruer: Calycozoa (Cylicozoa). Cup-shaped Acalepha attached by their aboral p)oh. They have four wide vascular pouches sejxirated by narrow walls, and eiyht arm- Uke processes beset with tentacles on the edge of the umbrella. The Calycozoa are best considered in their relation to the Scyhis- toma. They may be looked upon as Sr-yphistoma deprived of their tentacles, Avhich indeed are only transitory structures, and elongated so as to assume the form of a cup, and
. Elementary text-book of zoology, general part and special part: protozoa to insecta. Animals. :—caltcczoa. 057 ti) Sub-oruer: Calycozoa (Cylicozoa). Cup-shaped Acalepha attached by their aboral p)oh. They have four wide vascular pouches sejxirated by narrow walls, and eiyht arm- Uke processes beset with tentacles on the edge of the umbrella. The Calycozoa are best considered in their relation to the Scyhis- toma. They may be looked upon as Sr-yphistoma deprived of their tentacles, Avhich indeed are only transitory structures, and elongated so as to assume the form of a cup, and changed in several particulars which are characteristic, of the medusa stage. The four septa arise by the fusion of the four gastric folds with the Avide oral disc, which becomes drawn in and concave like a sub- umbrella. These four septa separate the same number of gas- " b. Fig. 197.—o, A Calycozoon (Luccrnar'.a) fvoTO. the oral surface maguified about 8 diameters. S, Septa of the four gastric pouches ; L, longitudinal muscle fibres ^T^th the genital band; Rt, marginal tentacles. I, The Calycozoon seen from the side ; G, Genital organs; Gn, gastric fold in the stalk; at the base is the foot gland. trovascular pouches; while the margin of the cup is drawn out into eight arm-like processes, from which groups of short, knobbed tentacles arise (fig. 197). The genital organs extend on the oral wall of the umbrella into the arms as eight band-shaped, plicated ridges. They run along in pairs at the lower part of each septum in the gastric cavity. The ovum, according to Fol, undergoes a complete segmentation, which i-esults in a single-layered blastosphere. This becomes an oval, two- layered larva, Avliich becomes ciliated, swims freely about, and finally attaches itself. The further development probably takes place < without alternation of generations. 17. Please note that these images are extracted from scanned page images that may have been digitally enhanced
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanimals, bookyear1892
