• Volume 20, Issue 4

      October 1944,   pages  115-142

    • Some observations on the breeding biology, and on the swelling, weight, water-content and embryonic movements in the developing, eggs, of the moluccan king-crab,Tachypleus gigas(MüLler) [arthropoda, xiphosura]

      M L Roonwal

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      1. Several hundred eggs of Tachypleus gigas (Müller) [ = Limulus mollucanus Latr.] were obtained on March 8 and 9, 1941 near Chandipore beach (Balasore District, Orissa, India) in a tiny creek arising from the R. Burhabalang close to its fall into the sea. They were brought over to Calcutta and studied alive for nearly a month which probably covers about one-half to two-thirds of the incubation period. Some 9 development stages, A-I, were recognized for reference.

      2. The eggs were laid in mud in the tidal zone in nests of over 100 eggs each. They were not carried on the abdominal appendages of the ♀ ♀ .

      3. The eggs are nearly spherical. They are first bounded by a thick, leathery chorion which later ruptures, exposing a thin, elastic euticula blastodermica. Their greatest diameter was measured and the volume calculated therefrom. The mean diameter of young eggs is 3·57 mm. in Stage A (2nd week of development), 3·86 mm. in C (shortly after the rupture of the egg-chorion) and 6·69 mm. in I or nearly double of the original in Stage A. The volume increases nearly 5 1/2 times. The swelling is due to the intake of water by the eggs.

      4. Between Stages A and I the mean wet weight of an egg increases from 24·17 mg. to 156·22 mg., or nearly 5 1/2 times. The mean dry weight rises from 14·20 to 18·02 mg., or by 26·9%. The water-content rises from 9·97 to 138·20 mg., or nearly 12 times, the greater part of the increase occurring after the rupture of the chorion.

      5. Embryonic movements, which begin in Stage F, consist at first of feeble leg movements which gradually become vigorous and are accompanied by continuous rotations along the antero-posterior and right-left axes of the embryo. The rotations are apparently caused by leg movements, and are not due to peristalsis or pulsations of the embryo.

    • On The submarine volcanic origin of rock-salt deposits

      K P Rode

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      From the foregoing treatment it is clear that though some salt deposits may possibly have been formed by simple precipitation in sea or lake waters, brought about by evaporation, lixiviation or by desiccation process, the formation of most of the principal salt deposits of the world is brought about by intra-tectonic submarine igneous activity in geosynclinal basins.

      This theory satisfactorily accounts for the various characteristics— chemical, structural, associational and distributional shown by most rock-salt deposits.

      If we now extend the scope of this theory, we can also apply it to the formation of certain other saline residues particularly the Borate and the Nitrate deposits, such as those of Chile, which show many characteristics in common with rock-salt.


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