Rnlght — 30 — Dictionary 



Coenospecies. — The total sum of possible combinations of a 

 genotype compound (Turesson). A variable hybrid of two 

 Linnean or ecospecies (Carpenter, 1938). 



Coenozygote. — The product of the fusion in fertilization of 

 two coenogametes. 



Cognation. — Kinship to a common pair of ancestors. 



Coil. — See Spiral. 



Coincidence. — The ratio of the number of double breaks 

 found to the number of double breaks which should occur 

 if there were no interference. This ratio is used as a measure 

 of interference in the crossing-over of chromosomes. 



Coition, Coitus. — Copulation, sexual intercourse. 



Colchicine. — CggHggOgN. An alkaloid obtained from Colchi- 

 cum autumnale used in medicine for lowering the uric acid 

 threshold of the kidney and in genetics to induce polyploidy. 

 Colchicine also occurs in the tubers of Gloriosa spp. "In 

 mitosis colchicine inactivates the spindle mechanism and delays 

 the division of the centromeres. Prophase stages ordinarily 

 show no irregularities. The nuclear membrane disappears but 

 no spindle develops and the condensed chromosomes . . . 

 form an irregular metaphase plate. After a few hours the 

 centromeres divide, but the daughter chromosomes, in the 

 absence of a spindle, do not pass to the poles ... A nuclear 

 membrane forms about them and the number of chromosomes 

 becomes doubled as a result of the longitudinal division" 

 (Beal, 1942). 



Collateral Inheritance. — A term used to describe the ap- 

 pearance of characters in collateral members of a family, as 

 when an uncle and a niece show the same character, inherited 

 by the related individuals from a common ancestor. Collateral 

 inheritance is characteristic of recessive characters which ap- 

 pear irregularly in contrast to dominant characters which do 

 not skip a generation in inheritance (J. Heredity). 



Colostrum. — The milk which is produced at the very begin- 

 ning of a lactation period and which contains more protein 

 and minerals than normal milk. 



Combining Ability. — The relative ability of a biotype to 

 transmit desirable performance to its crosses (Hayes & 

 Immer). 



General is "the average performance of a line 



in hybrid combination" and Specific is used to 



indicate "those cases in which certain combinations do rela- 

 tively better or worse than would be expected on the basis 



