516 GLOSSARY 



Geotropism (je ot'ro piz'm), response of an organism to gravity. 



Germ cells (jerni) (gametes), cells specialized for reproduction. 



Germ layer (jerm), one of the primary cell layers in an embryo. 



Germ plasm (jerm plazm), the hereditary material of an organism, the chromatin. 



Gills (gils) (pharyngeal clefts), a series of paired slits in the wall of the pharynx 



and body. 

 Gonads (gon'ads), reproductive organs. 

 Gonophore (gon'ofor), a reproductive individual which bears gonads, as in 



Hydroids. 

 Glochidlum (gl6 kid'ium), tlie larva of a fresh-water clam. 

 Glomerulus (glo mer'u lus), a body of capillaries enclosed at the end of eacli 



kidney tubule of the mesonephric and metanephric types of kidneys. 

 Glycerol (glis'erol), one of the alcohols which enters into the composition of 



fats; glycerin. 

 Glycogen (gli'ko jen), a form of carbohydrate food material as formed and stored 



by the liver. 



Habitat (hab'i tat), the place or area in which an animal or species lives. 



Haploid (hap'loid), the reduced or half number of chromosomes of the mature 

 germ cells. 



Heliotropism (he li ot'ro piz'm), a response of an organism to light. 



Hemoglobin (he mo glo'bin), a protein pigment substance of the blood which is 

 capable of absorbing oxygen and is red when combined with it. 



Hemolysis (he mol'i sis), disintegration of red blood corpuscles. 



Hepatic (hepat'ik), pertaining to the liver. 



Herbivorous (hur biv'6 riis), herb- or plant-eating animals. 



Hermaphroditic (hur maf ro dit'ik) (monoecious), having both male and female 

 germ cells produced in one individual. 



Heterozygote (het er 6 zi'g5t), an organism which is carrying sets of unlike char- 

 acters in its genetical constitution. 



Hibernation (hi ber na'shun), the cessation of activity or dormancy of an animal 

 during the winter season. 



Histogenesis (his to jen'esis), the development and differentiation of tissue cells. 



Histology (histol'oji), the science that treats of the microscopic structure of 

 the various parts of the animal body. 



Holoblastic (hoi 6 blas'tik), having the type of egg structure in which cleavage 

 divides the entire egg. 



Holozoic (hdlozo'ik), the animal nutrition, the ingestion and digestion of or- 

 ganic material. 



Homoiothermal (h6 moi'6 thur'mal), having a temperature regulation. 



Homolecithal (ho mo les'i thai) (isolecithal), eggs having a uniform distribution 

 of the yolk. 



Homologous (homorogus), similar in structure and origin, but different in 

 function. 



Homonomous (ho mon'6 miis), slight or no differentiation of body segments. 



Homozygote (homo zi'got), a zygote or resulting organism in which the corre- 

 sponding genes are alike. 



Hormone (hor'mon), the essential substance of an internal secretion which serves 

 to help in metabolism regulation. Produced by endocrine glands and 

 carried by the blood. 



Hyaline (hi'alin), semitransparent or glassy. 



Hybrid (hi'brid), a cross, or offspring of parents differing in genetical con- 

 stitution. 



Hydrolysis (hi drol'i sis), chemical rearrangement of a substance by combining 

 with water. 



Hydrostatic (hi dro stat'ik), a type of organ which regulates the specific gravity 

 of an aquatic animal. 



Hypertonic (hi per ton'Tk), possessing greater osmotic pressure than some related 

 substance. 



