Then
there are certain sponges, with the strange habit of making holes in
shells, and living in and on them. Sometimes the Oysters are stifled in
their "beds" by other Oysters settling and growing over them. Thick
masses of Mussels may cling to them and suffocate them. And grains of
sand sometimes get in the hinges of their shells, so that they cannot
close up the house when they wish.
Like the other animals which are useful as food, Oysters have been
carefully studied and cultivated by man for many, many years. The story
of the Oyster-beds is a long and interesting one.
Oysters feed in rather a strange way. You may have looked inside the
shells and seen two delicate dark-edged fringes, known as the "beard."
This fringe is the Oyster's gills or breathing arrangement. Trace the
"beard" as far as the hinge of the shells, and you see the mouth with
its white lips. If you could watch the creature having its dinner, you
would see a constant stream of water flowing over the gills and towards
the mouth.
What makes the water move in that way? The gills are covered with very
tiny lashes, like little hairs.
Pages:
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89