670 



COLLEGE ZOOLOGY 



particular gene, as contrasted with the reces- 

 sive trait, which develops only when both 

 members of a pair of allelic genes are alike. 

 We also speak of dominant and recessive 

 genes. 



Dor'sal (L. dorsum, back). Pertaining to the 

 back; opposed to ventral in a bilaterally 

 symmetrical animal. 



Duct ( L. ducere, to lead ) . A tube other than 

 a lympathic or blood vessel, through which 

 a liquid or other product of metabolism is 

 carried. 



Ducfless gland. Any gland that secretes a 

 substance (hormone) directly into the blood 

 or lymph stream, or both, instead of into a 

 duct; an endocrine gland. 



Du'o-de"num (L. duodeni, 12 each). The 

 first part of the small intestine posterior to 

 the stomach. It is so named because its 

 length is approximately 12 fingers' breadth. 



Du'ra ma'ter (L. dura, hard; L. mater, 

 mother). The outermost membrane cover- 

 ing the brain and the spinal cord. 



Ec'dy-sis (Gr. ek, out; dyein, to enter). Molt- 

 ing; the shedding of the outer cuticular 

 covering (skin) of an arthropod. 



E-coro-gy (Gr. oikos, house; logos, discourse). 

 The science of the interrelationships of or- 

 ganisms in and to their environment. 



Ec'to-com-men"sal (Gr. ektos, outside; L. com, 

 together; mensa, table). Pertaining to an 

 organism that lives on the external surface 

 of another organism, the host, without either 

 benefiting or injuring it. 



Ec'to-derm (Gr. ektos, outside; derma, skin). 

 The outer layer of cells in the gastrula. This 

 layer gives rise to the epidermis, sense or- 

 gans, and nervous system. 



Ec'to-par"a-site (Gr. ektos, outside; para, be- 

 side; sitos, food ) . A parasite that lives on the 

 outside of the body of its host. 



Ec'to-plasm (Gr. ektos, outside; plasma, some- 

 thing molded). The layer of cytoplasm near- 

 est the surface of a cell; the protoplasm of 

 the ectosarc. 



Ec'to-sarc (Gr. ektos, outside; sarx, flesh). The 

 structure in a protozoan composed of ecto- 

 plasm. 



Ef-fect'or (L. effectus, to effect). Any part of 

 the body, such as a muscle or gland, trans- 

 forming motor impulses into motor ac- 

 tion. 



Ef'fer-ent (L. efferre, to carry out). Conveying 

 outward or away from a structure. Opposite 

 of afferent. 



Egg (Probably L. avis, bird). The nonmotile 

 gamete developed by the female. 



E-jac"u-la-to'ry duct (L. e, out; jactare, to 

 throw). The duct conveying semen to the 

 urethra; especially in mammals. 



E-lec'tro-en-ceph"a-lo-gram' (Gr. elektron; Gr. 

 egkephalos, brain; Gr. gramma, letter). A 

 graphic record of the variations in the elec- 

 tric potential of a brain. 



E-lec'tron (Gr.). A particle of matter within 

 an atom, having little mass and a negative 

 charge. 



E-lec'tron mi'cro-graph (Gr. elektron. Gr. 

 micros, small; Gr. graphein, to write). An 

 enlarged photograph of an object taken by 

 attaching a camera to an electron micro- 

 scope. 



E-lec'tron mi'cro-scope (Gr. elektron. Gr. 

 micros, small; Gr. scopein, to examine). An 

 optical instrument in which a beam of elec- 

 trons focused by means of a magnetic field 

 (magnetic lens) is used to produce an en- 

 larged image of a minute object on a fluores- 

 cent screen or photographic plate. 



Em'bry-o (Gr. emhryon, from en, in; hryein, 

 to swell). A young animal that is passing 

 through its developmental stages, usually 

 within the egg membranes or within the 

 maternal uterus. 



Em'bry-og"e-ny (Gr. emhryon, embryo; 

 genesis, origin ) . The development of an or- 

 ganism. 



Em'bry-ol"o-gy (Gr. emhryon, embryo; logos, 

 discourse). The science which deals with 

 the development of an organism. 



Em'bry-o-nal (Gr. emhryon, embryo). Pertain- 

 ing to an embryo. 



En-am'el (O.F. esmaillier, to coat with 

 enamel). The dense white covering of the 

 crown of a tooth; the hardest substance pro- 

 duced in the animal body. 



En-cyst' (Gr. en, in; kystis, bladder). To be- 

 come enclosed in a sac (cyst). 



En-cyst'ment (Gr. en, in; kystis, bladder). The 

 process whereby an animal becomes en- 

 closed in an impermeable envelope. 



En'do-crine (Gr. endon, within; krinein, to 

 separate). Pertaining to the ductless glands. 



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

 The innermost layer of the early embryo 



