738 GLOSSARY 



auxin a plant growth substance, such as indoleacetic acid and related com- 

 pounds. 

 axolotl a form of salamander which retains some larval characteristics 



throughout life. 

 ^-galactosidase an enzyme that hydrolyzes ^-galactosides, such as lactose. 

 blastema a group of cells which will give rise to an organ or structure 



either during regeneration or in normal embryogenesis. 

 blastocoele the cavity of the blastula. 

 blastocyst the blastula of mammals. 

 blastula a stage in the early development of the embryo, consisting of a 



hollow sphere of cells. 

 bronchogenic originating in a bronchus (branch of the trachea). 

 C cytosine. 



Cannon bone either metacarpal or metatarsal bone of the horse. 

 carpel a flower organ which constitutes all or part of a pistil and in which 



seeds are produced. 

 cataphoresis the migration of suspended particles under the influence of 



an electric field. 

 cauline pertaining to the stem or of stem derivation. 

 centriole a cell organ usually present as two small chromatic granules in 



the cyptoplasm closely opposed to the nuclear wall. Plays a role in 



cellular division. 

 chelate a compound in which the same molecule is attached to a central 



atom at two different points, foiTning a ring structure, at least one such 



attachment being a coordinate linkage. 

 chelating agent a compound which can bind cations by forming stable 



complexes. 

 chemostat an instrument for maintaining growing microorganisms at a 



constant concentration. 

 chondrogenesis formation of cartilage. 

 chorioallantois an extra embryonic sac formed by fusion of the chorion and 



the allantois. 

 Circadian cycle the inherent diurnal rhythm shown by various physiologi- 

 cal processes and behavior patterns. 

 cis-trans test a genetic test to determine whether two characteristics are in 



the same functional unit (cistion). 

 clone all the descendants of a single individual. 

 contact exchange theory exchange of ions between soil surface and root 



surface. 

 corpora allata paired glands present in insects; they secrete the juvenile 



hormone. 

 cotyledons food-storage organs of a plant embryo; they may or may not 



persist in the seedling as photosynthetic organs. 

 c.p.m. counts per minute (emissions from a radioactive source). 

 cytokinesis the changes that occur in the cytoplasm of the cell during di- 

 vision and fertilization. 



