GLOSSARY 515 



Equatorial (ekwa to'ri al> plate, the platelike arrangement of chromosomes 



lying in the plane of the equator of the mitotic spindle during cell 



division. 

 Erepsin (erep'sin), an intestinal enzyme which splits peptones into amino acids. 

 Estivation (es ti va'shun), a dormant condition adopted by certain animals during 



summer. 

 Eugenics (u jen'iks), the science of genetics applied to human kind, usually for 



the purpose of improvement. 

 Euglenoid (u gle'noid), resembling a Euglena, as euglenoid movement. 

 Eustachian (usta'kian) tube, the tube extending from the middle ear to the 



pharynx. 

 Evagination (e vaj'i na'shun), the unequal growth outward of a surface layer, 



one of the processes by which , differentiation of organs is produced. 

 Eviscerate (e vis'er at), to remove or cast out the internal organs. 

 Exopodite (eks op'o dit), the external branch of the appendages. 

 Exoskeleton (ek so skel'e tun), the hardened parts of the external integument of 



an animal. 

 Expire (ek spir'), to expel water or air in the process of respiration. 



Factor (fak'ter), one of several interacting elements in a complex process. 



Agency influencing the development of an individual, as those carried 



in the genes of chromosomes. 

 Fauna (fo'na), a term referring to animal life. 

 Feces (fe'sez), the indigestible portion of the food which passes through the 



alimentary canal and is discharged by way of the anus. 

 Fertilization (fur tili za'shun), the union of a mature ovum and a mature 



spermatozoon to produce a zygote. 

 Fetus (fe'tus), an advanced stage of the embryo of a mammal before birth. 

 Fibrin (fi'brin), the fibrous material in a blood clot; formed when fibrinogen 



of the blood is exposed to air. 

 Filtrable virus (fil'trab'l vi'riis), an organism too small to be seen with the 



microscope and usually within cells of other organisms. 

 First filial (furst fil'i al) generation, the individuals arising from a particular 



mating. 

 Fission (fish'un), division of an organism into approximately equal parts. 

 Flagellum (flajel'um), a whiplike locomotor structure of a cell or single-celled 



animal. 

 Follicle (fol'ik'l), a cellular sac or pocket. 

 Fragmentation (frag men ta'slmn), a process by which individuals of certain 



Protozoa and simple Metazoa may divide internally to form several new- 

 individuals. 

 Freemartin (fre'mar tin), a modified female member of a pair of cattle twins 



which shows certain male features. 



Gametes (gam'ets). (See Germ cells.) 



Gametogenesis (gam e to jen'e sis), the series of cell divisions in the develop- 

 ment of germ cells. 

 Ganglion (gang'lion), a group of nerve cell bodies outside the central nervous 



system. 



Ganoid scale (gan'oid), rhombic in shape, composed of an inner layer of bone 

 and outer layer of enamel. 



Gastrula (gas'trob la), the two-layered stage in the development of an embryo. 



Genes (jenz), the units of material which function in the transmission of char- 

 Jictcrs in liGrGQitv. 



Genetics (jenet'iks), the science that treats of variation, resemblances, and their 

 inheritance from parent to offspring. 



Genotype (jen'otip), the genetic constitution of genetically identical organisms. 



Genus (je'nus), pi. Genera (jen'era), a division of the classification, a sub- 

 division of a family, and is divided into species. 



