496 APPENDIX 



Colony. An aggregation or intimate association of several or many 

 individuals to form a superior unit. 



Compound Eye. One composed of numerous facets, or separate visual 

 elements. Supposed to afford mosaic vision; e.g., in Crayfish and 

 Locust. 



Conjugation. Union (usually temporary) of two cells, resulting in fer- 

 tilization: e.g., in Paramecium. See Endomixis. 



Conservation of Energy. The ' law ' that the total energy of the universe 

 is constant, none being created or destroyed but merely transformed 

 from one form to another. 



Contractile Vacuole. A reservoir in unicellular organisms (e.g., Para- 

 mecium) in which water and waste products of metabolism collect and 

 are periodically expelled to the exterior. 



Cowper's Gland. Small ovoid body associated with the prostate gland 

 and urethra in the male of Mammals. 



Cranial Nerves. Nerves which arise from the brain. 



Cranium. The protective case enclosing the brain. 



Creatinine. A nitrogenous waste product. Present in small quantity in 

 human urine. 



Cretin. A defective individual, due to a deficiency of thyroid secretion. 



Crossing-over. The rearranging of linked characters as a result of the 

 exchange of homologous genes during synapsis of chromosomes. 



Crura Cerebri. Thickenings of ventral surface of mid-brain. 



Crustacea. A group of Arthropoda, including Crayfish, Crabs, etc. 



Cutaneous. Pertaining to the skin. 



Cuticle. The outermost lifeless layer of the skin. See Epidermis. 



Cyst. A resistant envelope formed about an organism (e.g., many Pro- 

 tozoa) during unfavorable conditions or reproduction. 



Cytology. The science of cell structure and function. 



Cytoplasm. Protoplasm of a cell exclusive of nucleus. Cytosome. 



Darwinism. Charles Darwin's theory of Natural Selection. Erroneously 

 used as synonymous with organic evolution. 



Decay. Chemical decomposition involving putrefaction or fermentation. 

 See Putrefaction. 



Dendrite. See Axon. 



Denitrifying Bacteria. Types of Bacteria which break down com- 

 pounds of nitrogen and set free the nitrogen to the atmosphere. 



Dermal. Pertaining to the skin. The dermis is the inner layer of the 

 Vertebrate skin. See Epidermis. 



Differentiation. A transformation from relative homogeneity to heter- 

 ogeneity, involving the production of specific substances or parts from 

 a general substance or part. Specialization. 



