438 APPENDIX 



their nuclei (pronuclei), by which the chromatin complex of each 

 is arranged to form the composite nucleus of the zygote. 



FLAGELLUM. A whip-like prolongation of the cytoplasm, the move- 

 ments of which usually effect the locomotion of the cell; e.g., 

 Sphaerella. 



FLOWER. A group of sporophylls and accessory structures, as in the 

 Flowering Plants. 



FLUCTUATIONS. Relatively slight variations always found in organ- 

 isms; may be either 'modifications or combinations. 



FOETAL MEMBRANE. The embryo of the higher Mammals before 

 birth lies in 'the uterus of the mother enclosed in a series of 

 membranes the outer one of which is in intimate contact with 

 the uterine wall at one or more points to form the placenta. 



FOVEA CENTRALIS. A slight depression at the posterior end of 

 the optical axis of the eyeball. The center of distinct vision. 



FROND. Fern leaf, usually both vegetative and spore-producing. 



FRUIT. The ripened ovule case and contents, together with any 

 structures which by adhesion become an integral part of it. 



GALL BLADDER. Receptacle near the liver for the temporary 

 storage of "bile. 



GAMETANGIUM. A gamete-producing organ, especially in the lower 

 plants. 



GAMETE. A cell which unites with another at fertilization to form 

 a zygote. Egg or sperm. 



GAMETOPHYTE. The sexual, gamete-bearing generation in plants. 



GANGLION. A. group of nerve cells, chiefly the cell bodies, with 

 supporting cells. 



GASTRIC VACUOLE. A droplet of fluid enclosing ingested food, in 

 which digestion occurs; e.g., in Paramecium. 



GASTROLITHS. Calcareous bodies found at certain times in the 

 lateral walls of the stomach of the Crayfish. Probably represent 

 the storage of material for the exoskeleton. 



GASTRULA. A stage in animal development in which the embryo 

 consists of a two-layered sac, ectoderm and endoderm, enclosing 

 the enteric cavity which opens to the exterior by the blastopore. 



GEL. A colloid which is more or less rigid. 



