. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 506 portion of the shell, and, before hardening, adheres to the fine particles with which it comes in contact. Into this case the eggs are laid, and in it the developing embryos are carried for many days. The eggs of this species are few, 20—70, large, 0,21 mm in diameter, and develop- ment proceeds slowly. Both Y. limatula and N. proxima throw the sexual products free into the water. The eggs are very numerous, smaller than those of N. delphinodonta (those. Fig. 8. Adult specimen of Nucula delphinodonta with egg case attache
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 506 portion of the shell, and, before hardening, adheres to the fine particles with which it comes in contact. Into this case the eggs are laid, and in it the developing embryos are carried for many days. The eggs of this species are few, 20—70, large, 0,21 mm in diameter, and develop- ment proceeds slowly. Both Y. limatula and N. proxima throw the sexual products free into the water. The eggs are very numerous, smaller than those of N. delphinodonta (those. Fig. 8. Adult specimen of Nucula delphinodonta with egg case attached, egg case is torn open to show the eggs inside. The of Y. limatula are 0,15 mm in diameter and those of N. proxima are 0,09 mm in diameter) and development is quite rapid. In all three forms, the cleavages are typical. Gastrulation of Yoldia, and probably of the other forms, is formed by epibole. At a rather early period the surface cells, or at least part of them, acquire cilia, and the em- bryos begin to roll around. In the case of N. delphinodonta, where the embryos are carried in a case, the embryos remain evenly ciliated, and are never able to swim freely. The embryos of both of the other species finally rise to the sur- face of the water and become quite 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 original Anatomische Gesellschaft. Jena : G. Fischer
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