Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] XIV. SPONGES Limy Sponge (Grantia). The sponge is the simplest of all Metazoa. One of the commonest forms is Grantia, a tiny urn-shaped object found in salt water attached to piles or stones. It is abundant in Island Sound. Long For this exercise have small vials containing specimens of Grantia preserved in formol or alcohol. The body is at- tached at one end. What do you find at the opposite end ? Label the hole the osculum. This l
Elements of biology; a practical Elements of biology; a practical text-book correlating botany, zoology, and human physiology elementsofbiolog00hunt Year: [c1907] XIV. SPONGES Limy Sponge (Grantia). The sponge is the simplest of all Metazoa. One of the commonest forms is Grantia, a tiny urn-shaped object found in salt water attached to piles or stones. It is abundant in Island Sound. Long For this exercise have small vials containing specimens of Grantia preserved in formol or alcohol. The body is at- tached at one end. What do you find at the opposite end ? Label the hole the osculum. This leads into a cavity called the cloaca. The wall of the Grantia, a limy sponge, on the shell of a mussel. From photograph loaned by American Museum of Natural History. body is pierced by a number of tiny holes or pores which communicate with the cloaca. The shape of the sponge is maintained by a skeleton composed of many tiny pieces or spicules of carbonate of lime. Notice the edge of the osculum. Make a drawing of the Grantia twice natural size, showing all the above structures.' An examination with the microscope shows the pores of the sponge to be lined with ciliated cells. These, by means of move- ments of the cilia, set up a current of water toward the cloaca. This current bears food particles, tiny plants and animals, which are seized and digested by the ciliated cells. T^. r . . These cells seemingly pass on the food to the Diagram of a simple sponge; ^ i ; o,ex- Other cells of the body. The middle layer halant opening or osciu- lum. 1 See Hunter and Valentine, Manual, page 159. 191
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