. Annotationes zoologicae japonenses / Nihon do?butsugaku iho?. 58o TAKU KOMAI : the micromeres are multiplying rapidly and gradually spreading over the macromeres (epiboly). Fig. 2 represents a stage in the above process, seen from the micromere pole of egg, where a moderately large elliptical gap exists between micromeres showing macromeres within. On the macromere pole too, there is in this stage another but somewhat smaller opening, which, however, is soon closed by the multiplying micromeres. The gap on the micromere pole persists for some time after the closure of the opening at the macr
. Annotationes zoologicae japonenses / Nihon do?butsugaku iho?. 58o TAKU KOMAI : the micromeres are multiplying rapidly and gradually spreading over the macromeres (epiboly). Fig. 2 represents a stage in the above process, seen from the micromere pole of egg, where a moderately large elliptical gap exists between micromeres showing macromeres within. On the macromere pole too, there is in this stage another but somewhat smaller opening, which, however, is soon closed by the multiplying micromeres. The gap on the micromere pole persists for some time after the closure of the opening at the macromere pole, but sooner or later it too comes to be closed. Directly after the closure of the gastrula at both its poles, there appear first traces of the aboral sense-organ, tentacles and ribs, as well as of the stomodaeal invagination, all nearly at the same time. The aboral sense-organ develops on the micromere pole and the stomodaeal invagination on the macromere pole, while the tentacles and ribs do so on the lateral region of the gastrula nearer the micromere than the macromere pole. Thus, the gastrula develops into a typical cydippid embryo. Cydippid Larva.—Fig. 3 shows an unhatched cydippid larva of a very early stage. The subspherical body exhibits at its one pole the mouth-opening (0) and at the opposite pole the sense-organ (s), besides a pair of tentacular rudiments (/) ard the eight comb-plate rows (c). The sense- organ, when viewed from above, is of a rhomboid outline with the longer diamètre in the sagittal plane of the larva; the otoliths forma small aggre- gation at both ends of the shorter diamètre. The polar plates can not yet be observed. The comb-plate rows as well as the tentacle -rudiments are located in the aboral half of the body. The former are arranged in four close pairs, each row containing Fig. 3 , •» C. o. Fig. 3. A young cydippid larva, seen on the tentacular plane, x 170. c. Comb-] late rows. o. Mouth aperture. oe. Oesophagus. ph. Phary
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Keywords: ., bookcentury1800, bookcollectionbiod, bookdecade1890, bookyear1897
