Knight — 148 — Dictionary 



the inheritance being received from the parent being progeny- 

 tested (cf. Lush, 1943). 



Testicle, Testis. — A male gonad; an organ within which 

 spermatozoa are formed. 



Testosterone, — acetate, — dipropionate, — propionate. 

 Testosterone is believed to be the hormone secreted by the 

 testis and responsible for the growth of the secondary sex 

 glands in the male (Robson). See Androgens. 



Tetrabasic. — Comprising four univalents. 



Tetracyte, — One of the four daughter cells formed by meiosis 

 from a mother cell. 



Tetrad. — (i) A group of four cells formed meiotically, e.g. 

 pollen tetrad, (ii) Four chromatids which together comprise 

 a bivalent at meiosis. 



Tetrad Divisions. — The first and second meiotic divisions 

 which the spore mother-cell undergoes to form four spores. 



Tetragenic. — Controlled by four genes. 



Tetraplant. — Tetraploid. 



Tetraploid. — Having four haploid sets of chromosomes in its 

 somatic cells; an organism of this type. 



Tetrasomaty. — The production of somatic nuclei with four 

 times the normal somatic chromosome number ; octoploidy. 



Tetrasome. — An association of four homologous chromo- 

 somes at meiosis. 



Tetrasomic. — An organism having one of its chromosomes 

 present four times in each somatic nucleus, the other chromo- 

 somes being present only twice, i.e. 2x -{- 2. 



Tetraster. — Used of cell division when a spindle mechanism 

 is formed having four poles. 



Thalamus. — The receptacle of a flower. 



Thanatosis. — A form of mimicry in which death is feigned. 



Theca. — A sheath covering an organ, particularly the layer 

 of ovarian connective-tissue stroma surrounding a Graafian fol- 

 licle. 



Theelin. — A female sex hormone. 



Theelol. — A female sex hormone. 



Thelygenic. — Producing offspring consisting entirely, or al- 

 most entirely, of females. N. Thelygeny. 



Thelykaryon. — The nucleus of a female gamete. 



Thelyplasm. Female cell-plasm as distinct from male proto- 

 plasm or arrhenoplasm, 



Thelytoky. — Parthenogenesis in which females only are pro- 

 duced. 



Thelytonic. — Parthenogenetic. 



