GLOSSARY 377 



Contractile vacuole. A vacuole whose contents ;ir(' pon'odicallj- ejected to the outside 



of the cell in which it is contained. 

 Copepod (ko' pe pod). Any one of a group of small Crustacea. 

 Copulation. The act of introducing spermatozoa into the body of the female. 

 Coracoid {kor' a koid). A bone of the ventral part of the pectoral girdle of vertebrate 



animals; a distinct bone in the bony fishes, amphibia, reptiles, birds, and lowest 



mammals, but fused with the scapula in t'he higher mammals. 

 Cornea. The transparent bulging membrane at the front of the eye. 

 Corpus luteum [pi., corpora lutea). A mass of cells invading the space in an ovary 



from which an ovum has escaped. 

 Corpuscle. One of the cells of the blood. 

 Cortex. The layer of gray matter which covers the cerebrum and dips into its 



folds. Also, an outer layer on various other organs, as the kidney or adrenal 



body. 

 Cranial nerve. One of 10 or 12 pairs of nerves arising from the central nervous system 



within the skull. 

 Craniosacral system. That part of the autonomic nervous system which centers in 



the brain and posterior portion of the spinal cord. Each organ controlled by the 



autonomic system is innervated once from it. 

 Cretaceous. Pertaining to the late Mesozoic time ; so named from the chalk deposits 



characteristic of it. 

 Cretinism. A developmental deficiency caused by inadequacy of the hormone 



thyroxin. 

 Crinoidea {kri noi' de a). A class of Echinodermata, including the feather stars and 



sea lilies. For definition see Chap. 19. 

 Crocodilini (krok' o di W ni). An order of Reptilia comprising the alligators and 



crocodiles and their allies. 

 Cro-Magnon {kro man yon'). A rather highly developed race of men preceding the 



principal races of today. It dwelt, as far as known, in Western Europe. 

 Crop. In the earthworm, an enlargement of the digestive tract behind the esophagus 



and in front of the gizzard. In birds, an enlargement of the esophagus for the 



temporary storage of food. 

 Crustacea. A class of arthropods including the lobsters, crabs, water fleas, barnacles, 



etc. For definition see Chap. 19. 

 Crystalline lens. A rounded, transparent, refractive body situated behind the pupil 



of the eye. 

 Ctenophora {te nof o ra). A group of animals of uncertain rank including the comb 



jellies and sea walnuts. For definition see Chap. 19. 

 Cubical epithelium. Epithelium in which the height and width of the cells are about 



equal. 

 Cuvier, Georges {ku vyay'). French naturalist, founder of comparative anatomy, 



1769-1832. 

 Cyclostomata {si' klo sto' ma ta). A class of Vertebrata having an eellike form, a 



cartilaginous skeleton, no jaws, and no lateral fins; lampreys and hagfishes. 

 Cytology. The science which deals with the structure of cells. 

 Cytoplasm. The protoplasm of a cell exclusive of the nucleus. 

 Cytosome. The body of a cell as distinguished from its nucleus. 



Darwin, Charles. Celebrated English naturalist, founder of the doctrine of natural 

 selection, author of several works on evolution. Lived 1809-1882. 



Deciduous. Falling off at maturity or at the end of a season ; said of the leaves of trees 

 which fall periodically. Applied also to trees whose leaves fall periodically. 



