Appendix A 327 



possess a character because neither of its parents carried the 

 possibilities for such a character in their germ-cells. 



Phenotype. The visible type of a group as expressed by 

 external characteristics. Opposed to genotype. There may be 

 several genotypes in a phenotype. 



Plateation. (From the Latin platea, meaning place.) A 

 physiological variation caused by external influences such as 

 locality, climate, soil, and so forth; sometimes called place- 

 variation. It is what Darwin called " definite variation." This 

 word was coined to express in one word the third of the three 

 kinds of variation fluctuation, mutation and plateation. (Here 

 first defined. A. W. G.) 



Quetelet curve. A curve which shows the relative frequency 

 with which individuals of a given lot, or population, occur in 

 certain classes. Class values are plotted on the horizontal 

 line and frequencies on the vertical. The mode is the highest 

 point of such a curve and represents the dominating type of 

 the character studied. 



Recessive characters. (See Dominant characters.) The 

 characters which are entirely covered up the first generation 

 but reappear the second and subsequent generations. 



Segregation. The reappearance in definite ratios, in the 

 second hybrid generation, of the characters of two forms crossed ; 

 and the first hybrid generation (when this differs from the 

 dominant character). 



Simplex. The condition of an individual which has inherited 

 a character from only one parent. 



Somatic. Of, or pertaining to, the body as opposed to the 

 germ-cells. 



Xenia. The results of a cross-fertilization between different 

 varieties of plants due to a double fertilization ; found in such 

 plants as corn, peas, etc. 



Zygote. The result of the union of two gametes. (See 

 Gamete.) 



