Quarterly Journal of Microscopical Science, Vol s3-91, 195-203, Copyright © 1950 by Company of Biologists

Studies of the Egg of Bacillus libanicus (Orthoptera, Phasmidae)

II. Moisture, Dry Material, and Minerals in the Developing Egg

¹ Hebrew University, Jerusalem

1. Weight, moisture content, and mineral content of freshly laid and of fully developed eggs of Bacillus libanicus (Uv.) were studied. During development of the embryo the egg-shell loses 19 per cent, of its initial mineral content, while the weight of mineral materials in the embryo increases correspondingly.

2. These changes can be explained only as resulting from transfer of minerals from the shell to the embryo. The mineral materials are derived from the calcium carbonate layer of the shell, which, owing to this loss, becomes thinner during embryonic development.

3. It is suggested that the mechanism of this transfer is based on the production of bicarbonate by the reaction of water and carbon dioxide, given off by the embryo, with the calcium carbonate of the shell.

4. Experimental calcium deficiency in the egg-shells results in a marked lowering of the viability of the embryos; although embryogenesis may sometimes proceed till the hatching stage, the few emerging nymphs survive only for a short time.

5. The possible occurrence of mineral transfer in other phasmid eggs is indicated.