The Canadian oyster : its development, environment and culture . h the older spat and adultoysters, they preserve a shining, dark, metallic lustre with a few faintradial lines (Plate IV, figs. 4, 5, 6). In the centre of the dorsal regioncan be distinctly recognized the larval shell (jDrodissoconch) of the oldestfree-swimming stage, presenting a uniformity of appearance in all thespecimens, and measuring in the neighborhood of 55 (=.38 mm.) inlength and slightly less in height. There is another way of verifying the size of the larva at fixation: viz.,to measure the prodissoconch of young spats;

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The Canadian oyster : its development, environment and culture . h the older spat and adultoysters, they preserve a shining, dark, metallic lustre with a few faintradial lines (Plate IV, figs. 4, 5, 6). In the centre of the dorsal regioncan be distinctly recognized the larval shell (jDrodissoconch) of the oldestfree-swimming stage, presenting a uniformity of appearance in all thespecimens, and measuring in the neighborhood of 55 (=.38 mm.) inlength and slightly less in height. There is another way of verifying the size of the larva at fixation: viz.,to measure the prodissoconch of young spats; but it is more liable to givesmall variations because of the pushing of the left umbo higher upwardsalong the substratum than the right, the addition of spat-shell overlyingthe edge of the larval shell, and also because this addition causes the edgesof the larval shell to be opened away from each other and the observer hasto look at a different angle upon their surfaces in different cases. A fewexamples of measurements are: COMMISSION OF CONSER\ATION Plate IV.

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Keywords: ., bookcentury1900, bookdecade1910, booksubjectoysterc, bookyear1913