xxxvi GLOSSARY OF TECHNICAL TERMS 



SEDIMENTABY (Lat. sedere, to settle down), a term applied to rocks 



deposited as sediment under water. 

 SEGMENTATION (Lat. segmentum, a cutting), division into parts, as 



in a dividing ovum or in the segmented body of a worm. 

 SEGEEGATION (Lat. segregare, to set apart), separating out. 

 SEMATIC (Gr. o-rj/xa, signal), a term applied to colours used as 



signals. 

 SEPALS (Lat. sepes, fence, enclosure), the modified leaves which 



form the outermost whorl (calyx) of a typical flower. 

 SILUEIAN (Lat. Silures, an ancient British tribe), one of the 



palaeozoic epochs, the characteristic rocks of which are 



largely developed in Wales, &c. (Siluria). 

 SOMA (Gr. o-w/xa, body), the body of an organism, contrasted with 



the germ cells. 



SOMATIC, pertaining to the soma or body. 

 SOMATOGENIC (Gr. <rw/xa, body ; rt. ytv-, origin), originating in the 



soma or body. 

 SOMATOPLEUEE (Gr. crw/xa, body ; vXtvpa, side), the body wall, 



enclosing the body cavity. 

 SOMITE (Gr. o-co/xa, body), one of the divisions of which a meta- 



merically segmented body is made up, = metamere. 

 SPECIES (Lat., sort, kind), a group of individuals which closely 



resemble one another owing to descent from common 



ancestors and at the same time differ from all other species 



(see p. 223). 

 SPECIFIC CHAEACTEES, characters by which one species is 



distinguished from others. 

 SPEEMAEY (Gr. (r-n-e'p/xa, seed, sperm), a general term for a gonad 



in which male gametes are produced (testis). 

 SPEEMATID (Gr. a-neppa, sperm), a cell which develops directly 



into a spermatozoon. 

 SPEEMATIST (Gr. a-nepua, sperm), an old term applied to one who 



believed that the animal embryo was produced entirely by 



the male. 

 SPEEMATOCYTE (Gr. o-Tre'p/xa, sperm ; KVTOS, cell), a cell from which 



spermatids, and hence spermatozoa, originate. 

 SPEEMATOGENESIS (Gr. mrep/xo, sperm ; yevecns, origin), the process 



by which male gametes (spermatozoa) originate. 

 SPEEMATOGONIA (Gr. o-n-e'p/xa, sperm; yovevs, ancestor), the cells 



from which the spermatocytes originate in spermatogenesis. 

 SPEEMATOZOID, a term sometimes applied to a plant spermatozoon. 



