GLOSSARY 909 



Diflferentiation (dif eren shi a'shun), the formation of special parts, tissues, or 

 cells from the primitive unspecialized layers. 



Diffuse (difus'), to mix with or to spread through completely and thoroughly 

 another substance. 



Digestion (di jes'chun), the conversion of complex unabsorbable food materials 

 into a form capable of bodily absorption. 



Dihybrid (dihi'brid), progeny or offspring of parents differing in two charac- 

 ters. 



Dominance (dom'inans), a condition in which one of two characters present 

 in the individual appears to the exclusion of the other. 



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 (di sim i la'shun). (See Catabolism.) 



Diurnal (diur'nal), active by day. 



Diverticulum (di ver tik'u liim), 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'todurm), 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 

 ectosarc of a protozoan animal. 



Ectosarc (ek'tS sark), the superiicial layer of cytoplasm of a single-celled 

 animal. 



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

 terial. 



Electrolyte (5 lek'tro lit), a substance whose molecules dissociate into ions. 



Electrotropism (e lek'trot'ro piz'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'd5krin), a sy.stem 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. 



Endcplasm (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 c^-toplasm within a cell which is surrounded 

 by ectoplasm; substance of this is endoplasm. 



Endoskeleton (en do skel'e tiin), the bony, cartilaginous, or other internal 

 frame work of an animal. 



Endothelium (en do the'liiim), the mesodermie lining laj'er of such closed 

 spaces as blood vessels and lymph spaces. 



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



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

 growth from the enteric cavity. 



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



