Changes in Specific Gravity of Atlantic Salmon (Salmo salar) Alevins

The specific gravity of Atlantic salmon (Salmo salar) alevins decreases during posthatching development from 1.067 at hatching to 1.044 at terminal yolk resorption. The water content of the embryo is ca. 84% throughout posthatching development while that of the yolk is ca. 56%. Therefore, as the embryo grows at the expense of yolk material, the water content of the alevin increases during development. This increase in water content can entirely account for the observed change in specific gravity. Alevins reared at lower temperatures have a higher specific gravity for any given embryonic length, implying the presence of more yolk reserves. Splake alevins reared in a hatchery tray had a lower specific gravity at a given length than did alevins reared in gravel or artificial turf substrates. Measurements of specific gravity in conjunction with length measurements during development may be useful in comparing different incubation conditions. Key words: specific gravity, Atlantic salmon, alevin, yolk, embryo, water content, temperature, splake

Performance of growing pigs fed dried microbial cells (Methylomonas methylotropha)

SUMMARYIn two experiments, 192 individually penned pigs were given diets containing 900 g barley/kg together with either 100 g dried microbial cells (DMC)/kg or 100 g white fish meal (WFM)/kg, and grown from 23 to 60 kg live weight. In Expt 1 rationing was by live weight and there was no difference between diets for feed used or live weight gained. In Expt 2, pigs were rationed by time and those fed diet DMC grew 15 g/day slower than those fed diet WFM, and their carcasses were of lower specific gravity.

Irregularly developed crystals of Zircon (sp. gr. 4.0) from Ceylon

Some small isolated crystals from the gem-washings in Ceylon, recently sent by Mr. A. K. Coomáraswámy to the British Museum for determination and study, were at first thought to be rutile, but on detailed examination proved to be zircon of a rather unusual type. This has a specific gravity of 4.0, which is not increased when the crystals are heated.The majority of the crystals are from the Balangoda district in the Sabaragamuwa province, and, according to Mr. Coomáraswámy have been derived from a group of zircon-granites which occur in this district; a few others are from Walaweduwa in the Bamberabotnwa district, and from the Hatton district. Associated with them are zircons of more usual types (see p. 48); the present description is, however, confined to the crystals of lower specific gravity.

A New Method for the Estimating the Specific Gravity of the Blood

The method of Roy for determining the specific gravity of the blood is a very excellent one, and is capable of yielding sufficiently accurate results. Over thirty bottles containing mixtures of glycerine and water of different specific gravity, ranging from 1·030 to 1·070, are used for the estimation, and a drop of blood to be tested is placed in a sample of one of these fluids. If the drop sinks it is heavier, if it floats it has a lower specific gravity, and then another drop of the same blood is tested until by a few experiments the exact specific gravity is determined.