566 GLOSSARY 



esophagus (es6f'agus). That part of the ahmentary canal lying between the 



pharynx and stomach; adj., esophageal (e so faj' e al). 

 estivation (es tl va' shtin). The assumption of a dormant condition by an animal 



during summer. 

 eu- (u). G.; true. 



eustachian (u sta' kK a,n) tube. A tube connecting the pharynx and middle ear. 

 evagination (e vaj i na' shiin). The protrusion by eversion of an internal surface, 

 evolution (6v 6 lii' shtin). Progressive development; adj., evolutionary, 

 ex- (&ks). G.; out of, ofT from, without. 

 excretion (6ks kre' shun). The passing out from a cell of a substance produced in it, 



this substance being waste to the cell and of no value to the body of which it is 



a part; also the substance itself; excretory (gks' kre to rl), pertaining to excretion. 

 exhalation (6ks ha la' shiin). The passage of gases outward from the lungs. 

 exoskeleton (6k so skSl' e ttin). An outer skeleton; adj., exoskeletal. 

 expiration (6k spi ra' shiin). The escape of carbon dioxide from the organism; or its 



passage from the tissues into the blood. 

 exteroceptor (6ks tur 6 s6p' tur). Sense organs for the reception of external stimuli. 

 extra- (6ks'-tra). L.; beyond, outside, 

 eye. An organ for vision. 

 eyespot. A ma.ss of pigment or a pigment-containing organ for the perception of 



light rays but not giving vision. 



Fi, F2, F3, etc. Abbreviations used in genetics and referring to successive filial 



generations. 

 family. Parents and their offspring; also a taxonomic group ranking between genus 



and order. 

 fat. An organic compound made up of a fatty acid and glycerin and containing 



carbon, hydrogen, and oxygen, with a relatively small number of oxygen atoms. 

 fauna (fo' na). A collective tei'm for the animals of a certain region; adj., faunal. 

 feces (fe' sez). The indigestible portion of the food which is passed through the 



alimentary canal and out of the body; adj., fecal, 

 -fer (fer). L. ; bearer, carrier. 



fertilization (fur tl II za' shun). The union of an egg cell and a sperm cell, 

 fetus (fe' tus). A young mammal after about one third of the time from the beginning 



of development to birth has elapsed; in the case of man, after the end of the third 



month; adj., fetal, 

 fibril (fl' bril). A slender fiber; or a component part of a cross-striated muscle fiber, 

 fibrin (fi' brin). The fibrous material in a blood clot; derived from the fibrinogen in 



the blood, 

 fil (fll). L.; a thread. 

 fission (fTsh' tin). The division of an organism into parts approximately equal in 



size, each part being a young organism, 

 flagellum (fla j6l' lim). A long whiplike structure attached to a cell; adj., flagellar, 

 fiame cell. A hollow cell containing a mass of vibratile cilia which carries on excretion 



in planarians and rotifers. 

 fossorial (f6 so' ri til). Fitted for digging. 

 fragmentation. An asexual method of reproduction in lower Metazoa in which the 



body divides into a number of parts each of which becomes an individual. 

 fraternal twins. Twins produced from two egg cells. 



Galen (ga' l6n), Claudius. Greek physician; 130-200? 



Galilei (gale la' e), Galileo. Italian astronomer; 1564-1642. 



gam (gSm). G., marriage. Gamet (g;1m' et). G., husband or wife. 



