674 Glossary 



Chordata — phylum that contains the vertebrates. 



Chorion — an embryonic membrane. 



Chromatin— deeply staining material that carries hereditary factors and which 



is located in the nucleus of the cell. 

 Chromatophore — a pigment cell. 



Chromosome— a dark-staining body formed during cell division. 

 Class— in classification, a category more inclusive than the order and less than 



the phylum. 

 Cleavage — first divisions of the fertilized egg. 



Coelenterata— phylum that contains the hydra, jellyfishes, and corals. 

 Coelom — a body cavity lined with peritoneum. 

 Colloid— a state of matter in which particles are distributed throughout a medium. 



The particles are larger than single molecules. 

 Colon — part of the large intestine. 

 Commensalism— a condition in which two organisms live together with neither 



benefiting or being injured. 

 Community — any assemblage of organisms. 

 Commissure — a connecting band of nerve fibers. 

 Condyle — a rounded protuberance on a bone. 

 Conjugation — temporary cytoplasmic union between two individuals accompanied 



by exchange of nuclear material. 

 Convergence — the development of similar characters between animals of diflfer- 



ent origins. 

 Copulation — sexual union, fusion of two gametes. 

 Corium — deeper layer of the skin ; the dermis. 

 Corpus callosum— band of nerve fibers uniting the cerebral hemispheres in the 



higher mammals. 

 Cortex — the outer part of an organ. 

 Cranium — the part of the skull which encloses the brain. 



Crop — enlargement of the digestive tract for the temporary storage of food. 

 Ctenophora — phylum of animals containing the comb jellies. 

 Cyst — a resistant sac which many small animals secrete about themselves to 



withstand unfavorable conditions. 

 Cytoplasm — protoplasm of the cell exclusive of the nucleus. 



D 



Dendrites — a process of a nerve cell which conducts impulses toward a cell body. 



Dentine — material which composes the principal mass of a tooth. 



Dermis — the deeper layer of the skin ; the corium. 



Diaphragm — in mam.mals, a muscle that separates the cavity of the chest from 



that of the abdomen. 

 Diaphysis — the shaft of a long bone. 

 Diastema — a space between teeth in a jaw. 

 Diarthrosis — a joint which permits free movement. 

 Diastole — dilation of the cavities of the heart. 

 Dihybrid — genetic cross involving two characters. 

 Dioecious — having the male and female reproductive organs in different individuals. 



