402 PRINCIPLES OF ANIMAL BIOLOGY 



Stylonychia {sti' lo nik' i a). A genus of ciliated protozoa. 



Subepithelial cells. In Hydra, rounded cells lodged among the epithelial cells, often 



near the base of the latter. 

 Sucker. An attaching organ beneath the head of a frog tadpole ; a similar organ on 



the scolex of a tapeworm colony; also the attacliing organ of leeches. 

 Sucrose. Common table sugar, a disaccharide derived from cane or beets. 

 Suctoria. A class of ciliated protozoa which bear no cilia when adult, but have tybe- 



like tentacles. 

 Surface phenomena. A group of physical and chemical phenomena characteristic 



of surfaces (of cells, particles, fine pores, etc.) 

 Sustentative {sus ten' ta tiv). Supporting; applied to connective tissue and other 



supporting tissues. 

 Suture. The line of junction between a septum of a cephalopod shell and the outer 



wall of the shell. Also the immovable joint between two flattened bones, as 



those of the skull. 

 Swammerdam, Jan {swahm' me?- dahm). Dutch naturalist, anatomist, and ento- 

 mologist, 1637-1680. 

 Sweat gland. One of the excretory organs of the skin. 

 Sylvius, Jacques Dubois. French anatomist, 1478-1555. 

 Symbiosis {sim' hi o' sis). The association of two species of animals for their mutual 



benefit. 

 Symbiotic. Of the nature of symbiosis. 

 Symmetry. The state of being symmetrical, or capable of being divided by a hne or 



plane into two parts which are mirrored images of each other. 

 Sympathin. A substance produced by nerve endings of the thoracolumbar sj^stem 



and serving to inhibit certain organs, stimulate others. 

 Synapse (sin aps'). The point of contact of two neurons. 

 Synapsis (sin ap' sis). The pairing of maternal with paternal chromosomes earlj- in 



the maturation of the germ cells. 

 Synapta. A genus of sea cucumbers. 

 Syncytium (sin sish' i urn). An undivided mass of protoplasm containing several or 



many nuclei. 

 Synonym (sin' o nim). A taxonomic name which is rejected because it is a duplicate. 

 Synura. A genus of colonial flagellate protozoa. 



System. A collection of organs concerned with the same general function, as diges- 

 tion. Also, the rocks, collectively, which belong to a geological period. 

 Systematic botany. See taxonomy. 

 Systematic zoology. See taxonomy. 

 Systemic circulation. The circulation of the blood through the body in general, as 



distinguished from that through the lungs or limgs and skin (pulmonary or 



pulmocutaneous) . 



Tadpole. The larva of a frog, or certain other animals. 



Tail. A slender posterior appendage. In a spermatozoon, the whiplike propelling 



organ behind the head and mid-piece. 

 Tamiasciurus (ta' mi a .sr n' rus). The subgenus of the genus Sciurus including the 



red squirrels. Sciurus (Tamiasciurus) hudsonicus loquax {hud son' i kus lo'- 



kwaks), the southern Hudsonian red squirrel. 

 Tarsal. One of a number of bones in the ankle of most vertebrate animals. 

 Tarsometatarsus (tar' so met' a tar' sus). A compound bone in the leg of a l)ini, 



formed of several of the metatarsals and tarsals. 

 Taxonomy. The science of the classification of animals or plants. 



