GLOSSARY 141 



Cestode. A parasitic flatworm consisting of a hooked head 



(scolex) and a segmented body (proglottides). The common 



tapeworm is a cestode. 

 Cilia. Microscopic hair-Hke protoplasmic processes from cells, 



which usually have the power of vibrating rhythmically. 

 Cocoanut pearls. Pearls from the oyster or clam of Singapore. 

 Coelom. A restricted term apphed to the body-cavity and other 



spaces in certain animals, which are formed in a distinctive 



manner. 

 Conch pearls. Pearls, often pink in colour, from the univalves 



Strombus and Cassis. 

 Conch shells. Univalves of the species Strombus and Cassis 



employed for making cameos. 

 Cyst pearls. True pearls which occur in the tissues of pearl- 

 producing shellfish, in a pearl sac and away from the shell. 

 Dead pearls. Pearls with practically only a lustreless and a dead 



white appearance. 

 Dorsal. The upper side of an animal as contrasted with the 



lower, or ventral side. The backbone side of vertebrated 



animals. 

 Drilled pearls. Pearls bored for mounting purposes. 

 Drop pearls. Oval pearls or pear-shaped pearls. 

 Dust pearls. Very small seed pearls. 

 Echinodermata (prickly-skinned). A group of marine radially- 



synnnetrical animals including the starfishes, sea urchins, 



sea cucumbers and featherstars. 

 Ectoderm. The epithelium bounding the outer surface of an 



animal's body, and its derivatives. 

 Epithelial sac. A sac composed of epithelium, as, for example, 



the pearl sac. 

 Epithelium. A layer of cells bounding a surface in the body of 



an animal, whether external or internal. 

 Fresh water pearls. Pearls from freshwater shellfish of the 



family Unionidae. 



