212 INVERTEBRATE ZOOLOGY 



Fertilization : the union of the spermatozoon and the ovum. 



Flagellum : a vibratory thread-like projection of certain cells ; hydroids, 



162, 166 ; sponges, 183 ; also of flagellate infusorians, 192. 

 Flame cell : the terminal cell of an excretory tubule of flatworms, 78. 

 Flexor muscle : a muscle that bends an organ, 37. 

 Food vacuole : a globule of water containing food particles ; Paramecium, 



186 ; Vorticella, 189 ; Amoeba, 195. 

 Front : the anterior median portion of the epicranium, 12. 

 Funiculus : a mesenteric strand connecting the stomach pouch with the 



body-wall in bryozoans, 86. 

 Funnel : the siphon of a cephalopod, 124. 



Ganglion : an aggregation of nerve cells ; grasshopper, 18 ; crayfish or 

 lobster, 41 ; crab, 44 ; Daphnia, 57 ; Nereis, 66 ; earthworm, 74 ; mussel, 

 97; clam, 111; snail, 121; squid, 133; Molgula, 138. 



Gastrolith : a calcareous body sometimes present in the stomach of crusta- 

 ceans, 40. 



Gastro-vascular space : the central cavity in Cnidaria ; Hydra, 160 ; tubu- 

 larian, 164 ; campanularian, 170 ; Gonionemus, 176 ; sea anemone, 179. 



Gastrula: a stage in the development of the embryo in which two cell 

 layers only are present, the ectoderm and the entoderm. 



Gena : the lateral portion of the epicranium in insects, 12. 



Genital plate : a sclerite at the posterior end of the abdomen in the male 

 grasshopper, 11. 



Giant fibers : three large fibers in the dorsal portion of the nerve cord in 

 the earthworm, 75. 



Gill : an organ for the breathing of air contained in the water ; crayfish or 

 lobster, 35 ; crab, 43 ; sow-bug, 47 ; amphipod, 49 ; Caprella, 50 ; Nereis, 

 63 ; mussel, 90 ; oyster, 100 ; clam, 104 ; squid, 127. 



Gill-filament : ciliated vertical ridges on the surface of the gills of lamelli- 

 branchs ; mussel, 94 ; clam, 108. 



Gizzard : a portion of the alimentary tract with thickened muscular 

 walls, 71. 



Glochidium : the larval form of Anodonta and Unio, which lives a parasitic 

 life in the skin of fishes, 97. 



Gonotheca : the cuticular outer covering of the blastostyle, 170. 



Green gland : the kidney of a malacostracan crustacean, 30. 



Haemal : pertaining to the blood system. 



Head : the anterior body-division of the higher animals. 



