. Pearls and pearling . and outside of the mantle produces a sortof milky liquid, containing carbonate of lime and animalmatter, which builds up the shell by thickening it fromthe inside and by adding to it at the edge, the pearlynacre near it, a layer of vertical prismatic cells outsidethis and over all, the protecting conchiolin the growth of the shell is only such as tomeet the needs of the growing animal and for its pro-tection. After the mussel reaches maturity, the shellceases to grow, excepting in some varieties which con-tinue to lay on nacre only. The mantle is ca
. Pearls and pearling . and outside of the mantle produces a sortof milky liquid, containing carbonate of lime and animalmatter, which builds up the shell by thickening it fromthe inside and by adding to it at the edge, the pearlynacre near it, a layer of vertical prismatic cells outsidethis and over all, the protecting conchiolin the growth of the shell is only such as tomeet the needs of the growing animal and for its pro-tection. After the mussel reaches maturity, the shellceases to grow, excepting in some varieties which con-tinue to lay on nacre only. The mantle is carried be-tween the locking hinge teeth and fills the space betweenthem like a cushion. In the illustration the mantle isfolded back to show other parts of the animal. A massof tough white muscular fibers will be found at each endof the shell on the inside near the back. These are thepowerful adductor muscles by which the animal closesthe shell. The muscles allow the shell to open but a short dis- The Life of the Unio 53. Fig. 5. Qitadrula heros, or Washboard mussel exposed. MA., mantle folded back to show the other proportions; M, mouth; P., palpi; F., foot; I. G., inner gill; O. G., outergill; B., branchial opening. tance so that the teeth always lock, and the mantlecushion swells when they are open and keeps them fromslipping. Inside of the mantle and hung along the hingeline is a sort of bag which contains the vital organs. Ittakes up a large space in the shell and is called the ab-dominal sac. This extends below and in front into atough muscular organ called the foot. The foot isshaped something like a tongue and can be projectedfrom the shell and worked into the ground. A good ideaof its use can be obtained by referring to Fig. 6, whichshows a Lampsilis rectus, or black sand-shell mussel plow- 54 Pearls and Pearling ing its way through the mud or sand. The foot holdsthe mussel up while it is feeding and is used to movethe animal from one place to another. By contractingand
Size: 1919px × 1302px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookidpearlspearli, bookyear1913
