GLOSSARY 



671 



which gives rise to the lining of the digestive 

 tract. Also called entoderm. 



En'do-par"a-site (Gr. endon, within; para, be- 

 side; sitos, food ) . A parasite living within the 

 body of its host. 



En'do-plasm (Gr. endon, within; plasma, 

 something molded). Within a cell, the cyto- 

 plasm that is surrounded by ectoplasm. 



En-dop'o-dite (Gr. endon, within; pous, foot). 

 The principal internal (medial) branch of 

 a biramous appendage of a crustacean. 



En'do-sarc (Gr. endon, within; sarx, flesh). 

 The structure formed by the inner mass of 

 protoplasm in a single-celled animal. 



En'do-sker'c-ton (Gr. endon, within; skeletos, 

 hard). A supporting structure on the inside 

 of an animal, whether it be cartilaginous, 

 bony, or of other material. 



En'do-some (Gr. endon, within; soma, body). 

 The central mass, consisting largely of 

 chromatin material, in the nucleus of certain 

 Protozoa. 



En'do-style (Gr. endon, within; stylos, pillar). 

 The ciliated groove in the ventral surface of 

 the pharynx in the amphioxus and some 

 other protochordates. 



En'do-the"li-um (Gr. endon, within; thele, 

 nipple). A cellular membrane that lines the 

 blood vessels, heart, and Ivmphatic vessels of 

 vertebrates. 



En'er-gy (Gr. energein, to be active). The 

 exertion of or the capacity for any particular 

 kind of work; ability to do work. 



En-ter'ic (Gr. enteron, gut). An adjective 

 form of enteron. 



En'ter-on (Gr. enteron, gut). The digestive 

 tract, especially that part derived from en- 

 dodcrm; zoologists often restrict use of the 

 term to intestine. 



En'to-derm (Gr. endon, within; derma, skin). 

 See Endodcrm. 



En'to-mol"o-gy (Gr. entomon, insect; logos, 

 discourse). The study of insects. 



En-vi'ron-ment (Fr. environ, about, there- 

 abouts). The place where a species of ani- 

 mals is found in nature and the conditions 

 that are present. The total of physical, 

 chemical, and biological conditions sur- 

 rounding an organism. 



En'zyme (Gr. en, in; zyme, leaven). A sub- 

 stance produced by living cells that causes 

 specific chemical changes such as hydrolysis, 

 oxidation, or reduction, but does not itself 



undergo significant change. It is a positive 

 catalyst, that is, it speeds up chemical reac- 

 tions. Pepsin and tripsin are enzymes which 

 help to split proteins into smaller molecules. 

 The human body probably contains thou- 

 sands of different enzymes. 



Ep-ib'o-Iy (Gr. epi, upon; ballein, to throw). 

 The posterior growth of a fold of the blasto- 

 derm over the surface of an embryo in the 

 process of forming the enteron during gas- 

 trulation. 



Ep'i-cra"ni-um (Gr. epi, upon; kranion, skull). 

 The largest sclcrite of the head in the grass- 

 hopper and related forms. 



Ep-i-der'mis (Gr. epi, upon; derma, skin). The 

 outer cellular layer or layers covering the ex- 

 ternal surface of a metazoan; it secretes the 

 cuticle on some animals. 



Ep-iph'y-sis (Gr. epi, upon; phyein, to grow). 

 The end of a long bone; also the pineal 

 body. 



E-pip'o-dite (Gr. epi, upon; pous, foot). A 

 long slender structure, fastened to the pro- 

 topodite of the walking leg of a crustacean. 



Ep'i-the"li-um (Gr. epi, upon; thele, nipple). 

 Usually a sheet of cells covering cither ex- 

 ternal or internal surfaces of the body. 



E'qua-to"ri-al plate (L. aequator, one who 

 equalizes). The platelike arrangement of 

 chromosomes in the plane of the equator of 

 the spindle during mitotic cell di\ision. 



E-rep'sin (L. eripere, to set free). An enzyme 

 mixture produced by the intestinal mucosa, 

 consisting of various peptidases which split 

 peptones and proteoses into simpler prod- 

 ucts; it has no effect on intact protein 

 molecules. 



E-soph'a-gus (Gr. oisophagos, gullet). The 

 gullet; the part of the digestive tract extend- 

 ing from the pharvnx to the stomach. Also 

 a part of the digestive tract of certain in- 

 vertebrates, though a pharynx and/or 

 stomach may not be present. 



Es'ti-va"tion (L. aestivus, pertaining to sum- 

 mer). A dormant condition adopted by cer- 

 tain animals during summer. Compare with 

 Hibernation. 



Eth'moid (Gr. ethmos, sieve; eidos, shape). 

 A small bone forming the upper \\all of the 

 nasal passageway. 



Eu-gen'ics (Gr. eu, well; genos, birth). The 

 application of the knowledge of heredity to 

 the improvement of the human species, 



