566 GLOSSARY 



Homologous (ho-mol'-o-gus), referring to body parts of animals that have the 



same embryonic and phylogenetic origin ; the parts may be on the same or 



different animals. 

 Homology (ho-mol'-S-ji), the relationship between body parts having the same 



embryonic and phylogenetic origin. 

 Homozygous (hom-5-zig'-us), bearing like genes. 

 Hormone (hor'-mon), a secretion of an endocrine gland that affects vital body 



reactions in higher animals. 

 Humerus (hu'-mer-iis), the bone of the upper part of the arm. 

 Hyper- (hi'-per), a prefix meaning "over" or "above". 

 Hypo- (hi'-p5), a prefix meaning "under" or "below". 

 Hypostome (hl'-po-stom), the projection at the oral end of Hydra that bears 



the mouth on its tip. 

 Hypothesis (hi-p6th'-e-sis), an assumption; a scientific possibility used as a 



basis for scientific investigation. 

 Hybrid (hi'-brid), an individual produced from parents of different genetic 



constitution. 



Ileum (ll'-e-um), the last portion of the small intestine in vertebrates; this 



comprises the greater part of the small intestine. 

 Iliac (Il'-I-ak), pertaining to the ilium, a bone of the pelvis. 

 Ilium (Il'-i-um), the anterior bone of the pelvic girdle. 

 In- (in), prefix meaning "in". 



Incisor (in-siz'-6r), a front tooth of mammals, designed for cutting. 

 Ingestion (In-jes'-chun), the taking in of food by an organism. 

 Insulin (ln'-su-lin), hormone from the pancreas. 

 Intracellular (in-tra-cel'-u-ler), within the cell. 



Invaginate (In-vaj'-i-nat), to fold in, as in the formation of the gastrula. 

 Ischium (ish'-i-um), the posterior bone of the pelvic girdle. 



Jejunum (je-ju'-num), the middle portion of the small intestine in vertebrates; 

 lies between the duodenum and ileum. 



Larva (lar'-va), an active immature stage found in the early postembryonic life 



of many animals. 

 Larynx (lar'-inx), the anterior portion of the tube carrying air to the lungs; 



contains the vocal cords when they are present. 

 Leucocyte (lu'-kO-sit), white blood corpuscle. 

 Ligament (lig'-a-ment), tough, elastic tissue connecting bones at the movable 



joints. 

 Littoral (lit'-o-ral), the shallow sea. 

 Lumbar (liim-bar'), pertaining to the region commonly called the "small of the 



back." 

 Lumen (lu'-men), the internal cavity of a duct. 

 Lymph (limf), the portion of the blood that circulates outside of the blood 



vessels; it contains no red blood corpuscles. 



Macronucleus (mak'-ro-nu'-kle-us), the large nucleus found in Paramecium. 

 Madreporite (mad'-re-p5-rit), a small disc on the aboral surface of starfish; it 



admits water to the water-vascular system. 

 Mandibular (man-dib'-u-lar), pertaining to the lower jaw. 



