GLOSSARY 195 



Per i car'di um, a membranous bag surrounding the heart. 



Per is so dac'tyl, ungulates with an odd number of toes 



Per'i to ne'um, a membrane that lines the body cavity. 



Pha'lanx (pi. phalanges), one of the bones of the fingers or toes. 



Phar'ynx, the region of the alimentary canal just back of the mouth cavity. 



Pigment, a substance which gives color to an object. 



Plan'ti grade, walking on the soles of the feet ; flat-footed. 



Pol'len has ket, the flattened hairy tibia of the hind legs of honey bees, used 



for carrying pollen. 

 Pol'lin na tion, the transfer of pollen from the anther of a flower to the stigma. 

 Polyp, any radially symmetrical animal, but usually an individual in a con- 

 nected colony. 

 Po rife ra, the sponges, distinguished by the canals which perforate the body 



wall. 

 Post em bry on'ic, development after birth or hatching. 

 Pos te'ri or, situated behind or toward the hinder part. 

 Pro bos'cis, a prolonged, flexible snout or a tubular structure, protruding 



from the head. 

 Pro'leg, an unsegmented appendage found in the larvae of some insects. 

 Protective resemblance, a method of protection due to the resemblance of 



an animal to its background. 

 Pro tho'rax, the most anterior division of the thorax. 

 Pro'to plasm, the living material composing the cell; the physical basis of 



life. 

 Pro to zo'a (sing, protozoon), animals of one cell, existing alone or in loose 



colonies. 

 Prox'i mal end, the attached end of anything which has also a free end. 

 Pulsating vacuoles, see Contracting vacuoles. 

 Pu'pa, the stage in the development of an insect immediately preceding the 



adult. 



Quill, one of the large, stiff, strong flight feathers or tail feathers of a bird ; 

 the hollow, basal part of a feather ; a large, hollow, sharp spine. 



Ra'dial sym'metry, having the organs or parts arranged symmetrically 

 around a center. 



Re gen er a'tion, the power to grow new parts or organs. 



Re'gions, the principal divisions of the body, head, thorax, and abdomen. 



Res pi ra'tion, the passage of oxygen into the tissues of a living organism and 

 of carbon dioxide out of them. These gases can pass through any thin, 

 moist, organic membrane. When such a membrane separates two fluids 

 which differ in the amount of oxygen they contain, oxygen passes to the 



