Glossary 677 



Homoiolhermic — having a relatively constant body temperature. 



Homology — similarity in evolutionary origins but not necessarily in function. 



Homozygous — having both genes identical for the same character. 



Hormone — the secretion of an endocrine gland. 



Hybrid — the offspring resulting from the union of two races. 



Hyoid — a group of bones at the base of the tongue which are developed from 



the second and third visceral arches. 

 Hypertonic — having a greater concentration of ions than another solution. 

 Hypotonic — having a lesser concentration of ions than another solution. 



I 



Heum — the longest part of the small intestine. 



Ilium — one of the bones of the pelvic girdle. 



Incisor — a type of tooth adapted for cutting. 



Insertion — the point of attachment of a m.uscle to the part to be moved. 



Integument — the covering structure of an animal. 



Intestine— portion of the digestive tract. 



Ion — a charged particle. 



Isogametes — gametes that are alike in size, motility, and appearance. 



Isodont — having teeth all alike. 



Isotonic — having the same concentration of ions as another solution. 



Jejunum — a portion of the small intestine. 

 Joint — articulation of two bones. 



K 



Keratin — a relatively insoluble protein found in the skin and its derivatives. 

 Kymograph — an instrument for the recording of muscular movements. 



Lacteal — a lymphatic vessel of the small intestine. 



Lacuna — a small cavity. 



Lamella — layer or plate. 



Larynx — upper part of the trachea. 



Lateral — pertaining to the side. 



Lateral line system — a series of sense organs along the sides of most fish and 



some larval amphibians. 

 Lethal — deadly. 

 Leucocyte — white blood cell. 



Ligament — a strand of connective tissue that joins two bones. 

 Liver — a large gland, usually associated with the digestive tract. 

 Lumen — cavity of a tubular organ. 

 Lung — a respiratory organ. 

 Lymph — a colorless liquid which circulates in the lymph vessels. It is derived 



from the blood and consists chiefly of blood plasma and leucocytes. 



