GLOSSARY 475 



Salivary glands. Glands whose secretion is discharged into the mouth 

 and usually has some digestive property. 



Sebaceous glands. Oil-secreting glands present in hair follicles. 



Secondary sexual characters. Traits other than the gonads that dis- 

 tinguish sexes. 



Secretion. The substance produced by a gland. The activity of a gland. 



Segmentation. See Metamerism. 



Sensory. Pertaining to sensation. Said of a neuron carrying impulses 

 from the periphery toward the central nervous system. 



Septum. Partition. 



Serum. The clear fluid remaining after blood has clotted. 



Sessile. Fixed; not free-swimming. 



Sex-linked characters. Characters whose genes are linked with those 

 of sex. 



Sol. A more or less fluid colloidal state. 



Solute. The substance dissolved in a liquid. 



Solvent. The liquid in which a substance is dissolved. 



Somatic. Pertaining to the soma or body as distinguished from germ cells. 



Species. A group of individuals derived from similar parents, or practically 

 alike in all important characters. 



Sperm. Male gamete. Spermatozoon. 



Spermatid. The male germ cell after the second maturation division but 

 before its transformation into a spermatozoon. 



Spermatocyte. The developmental stage of the male germ cell during 

 the growth period. 



Spermatogenesis. The development of a mature sperm from a primordial 

 germ cell. 



Spermatogonium. One of the products of the division of the male pri- 

 mordial germ cell. 



Spontaneous generation. Same as abiogenesis. 



Static. Pertaining to a body at rest or in equilibrium. 



Stimulus. Any disturbing influence producing a reaction in an organism. 



Stratum. A layer. 



Striation. Striping, such as the cross marks of skeletal muscle. 



Symbiosis. The association of two species of organisms for mutual benefit. 



Synkaryon. The fertilization nucleus formed by the union of male and 

 female germ nuclei. 



Systematise A student of taxonomy. An expert in classification. 



Tactile. Pertaining to the sense of touch. 



Taxonomy. The science of classification. 



Theory. A general principle serving as a plausible explanation of phe- 

 nomena, supported by facts and by relevancy of reasoning. 



Thorax. In mammals, the anterior division of the coelom separated from 

 the abdomen by the diaphragm and containing the heart and the lungs. 

 In arthropods, the middle body region. 



Thyroidectomy. The surgical removal of the thyroid gland. 

 Tissue. A group of histologically similar cells. 

 Traumatic. Due to a wound or injury. 



LltRARYJSa 



