The Canadian oyster : its development, environment and culture . onn appendix. The best that can be said for all references to a foot in these early stages is • hat, bycomparison with other species, they indicate the place where, at a later date, throughgro^\i;h and specialization, a foot as well as several other parts are formed between themouth and the anus; zoologists by inference from comparative embryology were pre-pared to find a rudiment or a vestige of this very characteristic molluscan organ. Mantle.—The mantle continues to grow downwards as two fleshyfolds right and left of the body
The Canadian oyster : its development, environment and culture . onn appendix. The best that can be said for all references to a foot in these early stages is • hat, bycomparison with other species, they indicate the place where, at a later date, throughgro^\i;h and specialization, a foot as well as several other parts are formed between themouth and the anus; zoologists by inference from comparative embryology were pre-pared to find a rudiment or a vestige of this very characteristic molluscan organ. Mantle.—The mantle continues to grow downwards as two fleshyfolds right and left of the body (Plate VI, figs. 1-9), to which they areattached along the dorsal region. The lateral flaps are thin and themargins free below, in front and behind. They lie against the inner sidesof the shell-valves and are responsible for the growth of the latter. Theedges form a thickened rim, containing unicellular glands, and supportingirregular processes resembling tentacles, that sometimes protrude beyondthe margin of the shell. COMMISSION OF COXSER^^\TIOX Plate II. Spat(Enlarged 50 times) KEY TO PLATE II Figs. 1-6. Oyster spats at different short intervals after fixation, forthe sake of space reduced to one-third the magnification of fig. 22 of PL I.,now magnified 50 diameters. The larval shell (prodissoconch) maintains the same size as long asit can be recognized in a spat. Larval shells of all spats maintain approx-imately the same size, no matter how large the spats grow. In all thefigures the prodissoconch is shaded, the dissoconch only outlined. The spats soon become so large that a lower power objective has tobe used in order to see the whole spat at once. Fig. 1. Spat with a very thin rim of new (spat) shell. Oc. 5, obj. 4 = 55 X 6-9--379 mm. Oc. 5, obj. 2 = 24 X 15-38= -369 mm. •369 X 50=18-5 mm. = approximately the length of the larval shellas it appears in the figures. Fig. 2. Spat -4 mm. long. Fig. 3. Spat -5 mm. long. Fig. 4. Spat -75 mm. long. Fig. 5. Spat 1 mm. long
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectoysterc, bookyear1913
