218 GLOSSARY. 



Gastro-vascular. Digestive and circulatory in function, as the gastro- 



vascular cavities of coelenterates. 

 Gastrozooid. Feeding individuals of hydroids. 



Genital atrium. A space receiving the genital ducts. See Bdelloura. 

 Genital gland. A gonad. 

 Genital plate. One of the plates through which the gonads open in 



echinoderms. 

 Genital pore. The opening in the genital plate or other external opening 



of a gonoduct. 

 Gill. Aquatic respiratory organ. 



Gizzard. A muscular triturating division of the alimentary canal. 

 Gonad. A generative tissue, a germ gland. 

 Gonangium. The transparent covering of gonophores. 

 Gonophore. The reproductive person of the colony that produces sexual 



products among hydroids. 

 Gonosome. The assemblage of structures directly connected with sexual 



reproduction in hydroids. The comprehensive term that includes 



gonophores, blastostyles, ovaries, gonangia, etc. 

 Green gland. One of the excretory glands of certain crustaceans. 

 Gullet. Esophagus; the tube leading back from the mouth or pharynx. 

 Gut. Digestive tube. 



Head. The anterior division of the body of higher animals 



Hepatic caecum. Digestive gland of a starfish. 



Hermaphrodite. With male and female sexual organs. 



Holophytic. The nutrition characteristic of plants. 



Holozoic. The nutrition characteristic of animals. 



Homologous. Of similar structure. 



Host. The animal that harbors a parasite. 



Hyaline. Transparent, glassy. 



Hydranth. An individual of a hydroid colony. 



Hydrocaulus. The stem of a hydroid colony. 



Hydrorhiza. The projections by which hydroid colonies are attached. 



Hydrotheca. The outer secreted covering or cup of a hydranth. 



Hypobranchial gland. A gland near the gill of some gastropods. Some 

 lamellibranchs have glands that bear the same name. 



Hypodermis. A cellular layer that lies just beneath the cuticle of anne- 

 lids, arthropods and some other animals. 



Hypopharynx. A projection borne on the lower side of the pharynx of 

 some insects. 



Hypophysis. A ventral projection from the brain of Chordata. 



