GLOSSARY 469 



tract), or that may be excretory in character (as in the metabolic prod- 

 ucts excreted by the kidney). 

 Glomerulus. A complicated network in the course of an arteriole of the 



kidney. 

 Glottis. A slitlike opening in the floor of the pharynx leading to the 



respiratory tubes and the lungs. 

 Glycosuria. The presence of excessive amounts of sugar (dextrose) in 



the urine. 

 Gonad. The organ in which germ cells develop. Ovary or testis. 

 Gustatory. Pertaining to the sense of taste. 

 Habitat. The natural abode of an organism; the kind of environment in 



which it lives. 

 Haploid. The reduced number of chromosomes. 

 Hemocoel. A body cavity which contains blood. A type of body cavity 



found in many invertebrates. 

 Herbivorous. Plant eating. 

 Heredity. The occurrence or production in offspring of parental traits 



or characteristics; the transmission of genes through the germ cells. 

 Hermaphrodite. An organism provided with both male and female 



gonads. 

 Heterocercal. Said of the type of fish tail in which the terminal part of 



the vertebral column takes an upward bend, making the tail fin asym- 

 metrical, the ventral portion much smaller than the dorsal. 

 Heterogony. The alternation of amphigony with parthenogenesis. 

 Heterozygote. An organism which has received from its parents two 



unlike genes for a given character and which, in turn, produces two 



numerically equal classes of gametes with respect to the genes. 

 Homologous. Said of organs having a similar origin in evolution 



though not necessarily a similar function. 

 Homoiothermal. Having a practically constant body temperature. 

 Homozygote. An organism which has received from its parents two like 



genes for any given character. Its gametes are, therefore, all alike 



with respect to these genes. 

 Hormone. An internal secretion of a gland which activates other organs, 



or the body as a whole, in a specific manner. 

 Host. An organism which harbors a parasite. 

 Hyaline. Glassy, translucent. 

 Hybrid. The offspring of parents, differing from one another in at least 



one heritable character. 

 Hydroid. Colonial coelenterate made up of individuals resembling Hydra. 



A polyp. 

 Hydrolysis. A double chemical decomposition reaction into which water 



enters. 

 Hydrostatic. Relating to the pressure and equilibrium of liquids. 

 Hyperglycemia. The presence of excessive amounts of sugar (dextrose) 



in the blood. 

 Hypertonic. Having a higher osmotic pressure than normal, or than 



another substance. 



