434 APPENDIX 



into particles larger than one molecule and suspended in another 



substance. 

 COLONY. An aggregation, or intimate association of several or 



many individuals to form a superior unit. 

 COMBINATION. Heritable variation due to recombinations of genes 



at maturation or fertilization. 

 CONJUGATION. The temporary union of two cells during which 



sexual phenomena occur; 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. 



Paramecium) in which water and waste products of metabolism 



collect and are periodically expelled to the exterior. 

 CORM. A solid bulb-like expansion of a plant stem below the surface 



of the ground. A bulb is an underground storage leaf bud. 

 COROLLA. The whorl of modified leaves immediately within the 



calyx of a flower. The petals collectively. 

 CORTEX. The cylinder between the outer and central cylinder in 



root and stem of the higher plants. 

 COTYLEDON. A seed leaf. The first leaf (in monocotyledons) or 



pair of leaves (in dicotyledons) of the young sporophyte within 



the seed. 



CRANIAL NERVES. Nerves which arise from the brain. 

 CRANIUM. The protective case enclosing the brain. 

 CROSSING-OVER. The rearranging of linked characters as a result 



of the exchange of genes during synapsis of chromosomes. 

 CRURA CEREBRI. Thickenings of ventral surface of mid-brain. 

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

 CUTICLE. The outermost lifeless layer of organisms. 

 CYST. A resistant envelope formed about an organism (e.g., many 



Protozoa) during unfavorable conditions or reproduction. 

 CYTOLOGY. The science of cell structure and function. 

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

 DECAY. Chemical decomposition involving putrefaction or other 



types of fermentation. 



