GLOSSARY 



335 



spermatid, sp'er ma fief (Gr. sperma, seed), a cell which is converted into a 



spermatozoon. 

 spermatocyte, sper'ma to sit (Gr. sperma, seed), a stage in the maturation of 



a spermatozoon. 

 spermatogenesis, sper'ma tojen'e sis (Gr. sperma, seed; gennao, I produce), 



the origin and development of spermatozoa. 

 spermatogonium, sper'ma togo'ni um (Gr. sperma, seed ; gonos, generation), 



a male germ cell just before maturation takes place. 

 spermatozoon, sper'ma tozo'on (Gr. sperma, seed ; zo on, animal) , a mature 



male germ cell, 

 spireme, spt'rem (Gr. speirao, wind round), the stage in mitotic nuclear 



division when the chromatin is in the form of a thread. 

 Spore, spor (Gr. spora, seed), a small reproductive body of certain animals, 

 statocyst, stat'o sist (Gr. statos, stationary; kustis,*. bladder), the organ of 



equilibration of the crayfish. 

 statolith, stat'o lith (Gr. statos, stationary; lithos, stone), a solid particle 



within a statocyst. 



steapsin, step' sin, a ferment which resolves fats into fatty acids and glyc- 

 erin. 



sterile, ster'il (L. sterilis, barren), not reproducing its kind, 

 sternum, ster'num (Gr. sternon, the breast), the ventral part of a somite of 



an arthropod, 

 stigma, s tig' ma (Gr. stigma, a mark), applied to spots of color, or to small 



openings. 

 stimulus, stim'u his (L. stimulus, a goad), something which evokes some 



functional or trophic reaction in the tissues on which it acts. 

 symbiosis, simbio'sis (Gr. sumbiosis, a living together), the living together 



of two different species of organisms (see p. 297). 

 systole, sis' to le (Gr. sustole, a drawing together), the period of time during 



which a rhymically pulsating vessel is contracted. 



telophase, tel'ofdz (Gr. telos, end), the last phase of mitotic cell division, 



during which the nuclei are re-formed, 

 telson, tel'son (Gr. telson, the end), the last joint of the abdomen of the 



crayfish. 



testis, tes'tis (L. testis, a witness), the male germ gland, 

 thermotropism, th'er mot'ropizm (Gr. thermo t heat ; trope, turn), reaction to 



heat. 

 thigmotropism, thig mot 'ro pizm (Gr. thigma, touch; trope, a turning), 



reaction to contact. 

 thorax, tho'raks (Gr. thorax, the breast), that part of the trunk situated 



between the head or neck and the abdomen. 



