514 • , GLOSSARY 



Dimorphism (di mor'fizm), difference of form between members of the same 

 species. 



Dioecious (die'shus), the male and female germ cells being produced by dif- 

 ferent individuals. 



Diploblastic (dip 16 blas'tik), composed of two germ layers. 



Diploid (dip'loid), having the base number or double number of chromosomes, 

 as in somatic cells. 



Dissimilation (disinii la'shun). (See Catabolism.) 



Diurnal (diur'nal), active by day. 



Diverticulum (di ver tik'u Mm), a blind tube branching out of a larger one. 



Duodenum (du 6 de'niim), the part of the small intestine between the stomach 

 and the jejunum. 



Ecdysis (ek'disis). (See Molt.) 



Ecology (ekol'oji), the science of the relation of an organism to its environ- 

 ment. 



Ectoderm (ek'to durm), the outer cell layer of the wall of a gastrula and its 

 later derivatives. 



Ectoplasm (ek'to plaz'm), substance of the outer layer of cytoplasm or ecto- 

 sarc of a protozoan animal. 



Ectosarc (ek'to sark), the superficial layer of cytoplasm of a single-celled 

 animal. 



Egestion (ejes'chun), the casting out by the body of indigestible food ma- 

 terial. 



Electrolyte (e lek'tro lit), a substance whose molecules dissociate into ions. 



Electrotropism (elek'trot'ropiz'm), response of an organism to electric cur- 

 rents. 



Embryology (em bry ol'o ji), the science of the origin and development of the 

 individual. 



Endocrine system (en'dokrin), a system including those ductless glands which 

 secrete hormones. 



Endoderm (en'do durm), the inner cell layer of the wall of the gastrula and its 

 later derivatives. 



Endomixis (en do mik'sis), nuclear reorganization within a protozoan which 

 does not involve conjugation. 



Endoplasm (en'do plaz'm). (See Endosarc.) 



Endopodite (en dop'6 dit), the internal or principal branch of a biramous ap- 

 pendage of Crustacea. 



Endosarc (en'do sark), the area of cytoplasm within a cell which is surrounded 

 by ectoplasm; substance of this is endoplasm. 



Endoskeleton (en do skel'e tun), the bony, cartilaginous, or other internal frame- 

 work of an animal. 



Endothelium (en do the'li um), the mesodermic lining layer of such closed spaces 

 as blood vessels and lymph spaces. 



Enteric (en'terik), adjective form of enteron. 



Enterocoele (en'ter 6 sel), a portion of the coelomic cavity that arises by out- 

 growth from the enteric cavity. 



Enteron (en'ter on), a digestive cavity or tube. > 



Entomology (en'tomol'd ji), the branch of zoology that deals with the study of 

 insects. 



Entozoic (en'to zo'ik), forms which live within the bodies of other animals. 



Enzymes (en'zimz), substances that bring about chemical transformation. , 



Ephyra (ef'i ra), tlie free-swimming larval form of the Scyphozoa. 



Epiboly (epib'oli), posterior growth of a fold of the blastoderm over the sur- 

 face of an embryo in the formation of the enteron during gastrulation. 



Epigenesis (ep i jen'e sis), the conception that the parts of the organism arise 

 from an undifferentiated germ cell. 



Epithelium (ep'i the li um), a sheet of cells covering an internal or external 

 surface of the body. 



