GLOSSARY 173 



palp (palpus). In arthropods a feeler, especially the jointed 



palps on the mouth parts; in the clam soft, fleshy, 



ciliated flaps near the mouth, 

 parapodium. A fleshy unsegmented appendage of a somite 



of annelids, 

 parenchyma. The soft cellular tissue of plants and animals. 



In the fern the pith; in flatworms the soft tissue which 



fills the body cavity, 

 pectoral. Of or pertaining to the breast or chest, as pectoral 



muscles, pectoral girdle, 

 pelvic. The girdle, in vertebrates, which attaches the hind 



legs to the vertebral column. 



pericardium. The membrane which surrounds the heart, 

 perisarc. The protective, horny, secreted sheath about 



hydroids. 

 peristome. A lip around the mouth in Vorticella and other 



protozoa, 

 peritoneum. A smooth serous membrane which lines the 



body cavity and covers the viscera, 

 photosynthesis. The process by which starch is manufactured 



in green plants, in the presence of sunlight, 

 planula. The larva of many Coelenterates; it is usually 



oval in form and covered with cilia, 

 plasmolysis. The separation of the protoplasm of a cell from 



its enclosing cell wall, 

 plexus. An aggregation of vessels or nerves forming an 



intricate network, 

 polyp. An organism or a part having a structure similar to 



that of the fresh water hydra, 

 posterior. At or toward the hind or tail end. 

 proboscis. The long flexible sucking mouth parts of the bee. 



