GLOSSARY 405 



Sporophjrte (spo' rofite). The asexual generation of certain plants; so called because 

 it rt'produces by means of spores. 



Sporosac [fspo' ro sak). An abortive medusa, as in Hydractinia. 



Sporozoa {spo' ro zo' a) . A class of Protozoa, parasites usually without locomotor 

 organs or mouth. 



Sporozoite ispo' ro zo' ite). One of the minute cells contained in the cysts of Coccidium 

 schubcrgi and similar parasites. These cells escape when the cyst is swallowed by 

 the host. 



Sporulation {spor' u la' shun). The formation of spores ; sometimes applied to multiple 

 division of the nucleus followed by fragmentation uf the cj^toijlasm, which occurs 

 in the spore-formation of certain species. 



Squamosal {skiva mo' sal). A bone of the postero-lateral region of the skull of verte- 

 brates. In the mammals it suspends the lower jaw, but not in the other verte- 

 brates. 



Squamous epithelium (skwa' mus). Epithelium whose cells are low and flat. 



Statoblast {slat' o blast). A gemmule-like body bj^ means of which many Bryozoa 

 reproduce asexually. 



Steapsin {ste ap' sin). The fat-splitting enzyme of the pancreatic fluid. 



Stearic {ste ar' ik). One of the very common fatty acids. 



Stegocephali {steg' o sef a li). A group of extinct armored Amphibia of huge size. 



Stegodon {steg' o don). A genus of extinct animals, ancestral to the elephants, from 



the Pliocene of southern Asia. 

 Stegosaurus {steg' o saw' rus). A genus of dinosaurs bearing rows of plates set 



vertically on the back; belonging to Jurassic and Comanchian time. 



Stejneger {sti' neger). A living American herpetologist. 



Stentor {sten' tor). A genus of ciUated Protozoa. 



Sternum {ster' num). The breast bone; present in most vertebrates except fishes 

 and some reptiles. 



Stigma {stig' ma). A pigment spot in certain unicellular organisms, sometimes 

 regarded as hght-perceptive. Also, the part of the pistil of a flower which receives 

 the pollen. 



Stimulus {stim' u lus). A change in the environment or some internal condition 

 which produces a reaction in an organism. 



Stomach {stum' ah). An enlargement in the anterior part of the digestive tract of 

 many animals; certain phases of the digestion of food occur there. 



Stomodaeum {sto' mo de' um). That part of the mouth which originates from an 

 invagination of the ectoderm. 



Stratified {straf i fide) . Arranged in strata or layers; said of epithelia, geological 

 deposits, etc. 



Stratum {stra' turn) {pi., strata). Alayer; specificially, a layer of sedimentary rock. 



Stratum corneum {stra' twn kor'neum). The thin outermost layer of cells in the 

 skin of certain animals (as the frog). 



Striated muscle {stri' a ted). Muscle composed of cylindrical, cross-banded, multinu- 

 cleate cells (except in the heart). Skeletal muscles in vertebrates are of this kind. 



Striation {stri a' shm). A stripe; as the cross-lines of volimtary muscle cells. 



Structural formula {striik' tu ralfor' mu la). A formula designed to show the arrange- 

 ment of atoms in the molecule of a chemical substance. Also called graphic 

 formula. 



