448 ELEMENTS OF BIOLOGY 



Gamete. A germ cell, either ovum or sperm. 



Gametic reproduction. The reproductive process that involves germ 

 cells. 



Gametophyte. The stage in the life history of mosses, ferns and seed- 

 bearing plants which produces gametes and reproduces by a sexual 

 process. 



Ganglion. An aggregation of nerve cells. 



Gastrulation. The process of conversion of the blastula stage into the 

 two-layer gastrula. 



Gene. A system located in the chromosome that determines the de- 

 velopment of an inheritable character. 



Genotype. The genetic make-up of an individual. To express the geno- 

 type of the individual is to state the various genetic characters which 

 that individual is capable of transmitting to its progeny. 



Germ plasm. A general term applied to the reproductive cells, especially 

 with reference to their properties in conveying inheritable charac- 

 ters. 



Gizzard. A modified region of the gut tract particularly adapted to the 

 abrasion of foods by the action of the wall muscles and the contained 

 abrasives such as sand. 



Glomerulus. Small bodies in the mesonephros and metanephros in 

 v/hich the essentials of the process of excretion occur. 



Glycogen, A carbohydrate occurring in the liver and in muscle. 



Gonad. The structure, either ovary or testis, in which the germ cells 

 develop. 



Graafian follicle. A structure in the mammalian ovary within which 

 the egg matures. 



Graviotropism. Response to gravity. 



Green glands. The excretory glands of Crustacea. 



Growth. Increase in size as a result of metabolism. 



H^MOCYAN. A green copper-containing substance occurring in the bloods 

 of most Mollusca, Arthropoda, and some other invertebrates. 



Haemoglobin. The red agent in the blood of a few molluscs, annelids, 

 and vertebrates that is responsible for the blood color. Its function 

 is primarily the transfer of oxygen and carbon dioxide. 



HEMOPHILIA. A state of the blood in which it does not clot in the nor- 

 mal manner. 



Haploid NUMBER. The number of chromosomes characteristic of the 

 mature germ cell; one-half the diploid number. 



