APPENDIX I 



Congenital, of a character of an individual recorded at birth or 

 referable to constitution at birth. Either of genetic or environmental 

 origin. 



CoNGRESSiON, the movement of chromosomes onto the metaphase plate, 

 especially at the first meiotic division. Darlitigtoii 1937. 



Conjugation, the pairing of gametes or zygotes, or the fusion of pairs 

 of nuclei. 

 Conjugation of Chromosomes, side-by-side association of chromo- 

 somes in the early prophase of meiosis (f. Pairing, Zygotene). 



Constriction, an unspiralized segment of fixed position in the meta- 

 phase chromosome. Agar 1911. 

 Nucleolar Constriction, a secondary constriction determined by 



the organization of a Nucleolus. Darlington 1937. 

 Primary (or Centric) Constriction, one associated with, and deter- 

 mined by, the Centromere. Darlington 1937. 

 Secondary Constriction, any Acentric constriction, either Nucleolar 

 or Heterochromatic. Darlington 1926. 



Contact Points, places where the chromosomes first come together 

 in pairing at Zygotene, v. Locahzation, Polarization. Darlington 1940. 



Contingency Table, a table of frequencies showing two classifications 

 simultaneously, and used in testing their independence. 



Continuity, Yates' Correction for, a correction applied in the 

 calculation of Normal Deviates or x^'^ to allow for the discrepancy 

 arising by the observations being discontinuous while tables of 

 the Normal Deviate and x^ ^^e calculated on the supposition of 

 continuity in the variate. 



Convergent Improvement, the simultaneous improvement of two inbred 

 strains by recurrent back-crosses of their hybrid to each strain in 

 separate lines, selection being practised for the desirable features of 

 each strain in that line of wliich it is not the recurrent parent. 



Co-ORLENTATiON, V. Orientation. 



Correlated Response, change in one character due to selection for 

 another. Due either to pleiotropy of one gene or to linkage of 

 several genes concerned. Wigan and Mather 1942. 



Correlation, the interdependence of variates. The opposite of indepen- 

 dence. AppHed also to the analysis of such interdependence by 

 methods involving the two variates symmetrically. Cf. Regression. 

 Correlation Coefhcient, the ratio of the covariance of two variates 

 to the geometrical mean of their variances. Ranges from + i to — i. 

 Partial Correlation, the correlation of certain variates when due 

 allowance is made for the effects of other uncontrolled variates. 



Elements of Genetics 3 " 5 ^^ 



