232 GLOSSARY 



Auricle : a chamber of the heart which receives the blood from the veins. 

 Avicularium : a structure shaped like a bird's head attached to the zooecium 

 in Bryozoa. 



Balancers: the homologues of the metathoracic wings in Diptera. 

 Bilateral symmetry: having the right and left sides alike. 

 Bivalve : a shell composed of two distinct and equivalent parts or valves. 

 Bivium : the two rays of a starfish or a sea urchin which inclose the madre- 



porite between them ; the two rays forming the upper side of the holothu- 



rian's body. 

 Blastostyle: the reproductive polyp of a campanularian hydroid. 

 Body cavity: an internal space in the body in which lie the viscera ; thecoelom. 

 Body wall : the outer portion of the body, which usually bounds the body 



cavity toward the inside. 

 Brachial : relating to the arms. 

 Branchial: relating to the gills. 

 Branchial heart: a lateral heart in the squid. 

 Branchiate : bearing gills. 



Branchiostegite: a paired lateral fold of the body wall in crustaceans. 

 Brood sac: a chamber in which the eggs develop in certain crustaceans. 

 Bud: an outgrowth of an animal which becomes a new individual. 



Caecum: a saclike appendage of the digestive tract. 



Calcareous: formed of carbonate of lime. 



Carapace: the shell covering a portion or all of the cephalothorax in 



crustaceans. 

 Cardo : the basal division of the maxilla in insects. 

 Cellulose: the woody cell wall of plant cells. 

 Cephalothorax: a body division formed by the fusion of the head and the 



thorax in arthropods. 

 Cercus: a paired projection at the posterior end in certain insects. 

 Cerebral: relating to the cerebrum, or brain. 

 Cheliped: the large grasping claw in many crustaceans. 

 Chitin: a hard and very resistant substance present in the cuticula of 



arthropods. 

 Chloragogue cells: glandular cells surrounding the digestive canal of the 



earthworm. 

 Chlorophyll: the green coloring matter of plants. 

 Chromatophores: pigment bodies. 



Cilia: the numerous vibratory projections on the surface of certain cells. 

 Cirrus: a filamentous, sensory appendage of annelids; a protrusile, copu- 



latory organ of flatworms. 

 Clitellum: a thickened, glandular region on the earthworm which secretes 



the cocoon. 



