GLOSSARY 517 



Hypostome (hi'po stom), a conical projection around and below the mouth in 

 coelenterates. 



Hypothesis (hi poth'e sis), an idea as it first develops as the result of prelimi- 

 nary observation and experiment. 



Ileum (il'eum), the posterior and longest part of the small intestine. 



Ilium (il'ium), dorsal bone of pelvic girdle of terrestrial vertebrates. 



Immunity (i mu'ni ti), freedom of susceptibility to disease. 



Ingestion (in jes'chiin), the taking in of food material by an organism. 



Insectivorous (in sek tiv'6 rus), insect-eating animals. 



Inspire (in spir'), the drawing in of water or air in the respiration. 



Instar (in'star), the period between molts in insect development. 



Insulin (in'sti lin), a hormone produced by the pancreas and essential to the 



proper metabolism of carbohydrates. 

 Integration (in te gra'shun), development and correlation to give unity in an 



organism. 

 Integument (in teg'u ment), the outer covering of the body. 

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

 Intracellular differentiation (in tra sel'u ler dif er en shi a'shun), the presence of 



a variety of cells within one l^ody. 

 Invagination (in-vaj i na' shun), the unfolding process by which the primary 



endoderm is withdrawn into the blastular cavity and becomes enclosed 



by the primary ectoderm. 

 Irritability (ir i ta bil'i ti), the capacity of protoplasm for responding to changes 



in environmental conditions or to external stimuli. 

 Isolecithal (i so les'i thai). (See Homolecithal.) 

 Isotonic (isoton'ik), possessing the same osmotic pressure in related substances. 



Jejunum (je jobnum), the middle division of the small intestine, between the 

 duodenum and the ileum. 



Karyokinesis (kar i 6 ki ne'sis), mitotic cell division. 

 Karyolymph (kar'i o limf), the more fluid material of the nucleus. 

 Karyoplasm (kar'i 6 plaz'm), the protoplasm which constitutes the nucleus. 

 Karyosome (kar'iosdm), a -''net knot" or a part of the chromatin which forms 



a distinct body in the nucleus. 

 Katabolism (ka tab'6 liz'm). (See Catabolism.) 

 Keratin (ker'atin), a nitrogenous substance forming the chemical foundation 



of hair, horn, feathers, nails, claws, etc. 

 Kinetic energy (ki net'ik), energy inherent in motion of a body. 



Labium (la'bium), posterior boundary or lower lip of an insect's mouth. 

 Labrum (la'brum), the exoskeletal anterior boundary or upper lip of the insect's 



mouth. 

 Lacrimal (lak'rimal), pertaining to tears. 

 Lacteal (lak'teal), pertains to milk; refers to lymphatics of the intestinal 



region because of their light colo"!* following absorption of fat. 

 Lacuna (lakii'na), a cavity or space, particularly that of bone, which contains 



the bone cells. 

 Lamella (la mel'a), a thin layer or plate. 



Larva (lar'va), the young stage of an animal, which changes form during life. 

 Larynx (lar'inks), the expanded upper end of the windpipe or trachea; voice 



box. 

 Lethal (le'thal), capable of producing death. 

 Leucocyte (lu'kosit), a white blood corpuscle. 

 Ligament (lig'ament), a band of white fibrous connective tissue connecting 



structures other than muscles; particularly joining bones at the joints. 

 Limpet (lim'pet), a small type of gastropod (Mollusca) with a simple uncoiled 



shell, 



