GLOSSARY 315 



Ovum. The animal female sex cell, which, when fertilized by the male sex 

 cell, is capable of developing into a new individual. Plural, 07'a. 



Pedigree. The ancestry of an animal or plant; especially the list of the 

 names and registry numbers. 



Pedigree register. The official publication in which pedigrees are printed, 

 each breed having its own. 



Physi(^ogical unit. A term used by Galton and others to denote those 

 ultimate particles of living matter that determine characters, covering the 

 same general conception that later was covered by Weismann with his more 

 minute distinctions of biopheres, ids, and determinants. 



Pollen. The male sex cells of higher plants. 



Pollen grain. A single cell of pollen. 



Progression. Advance as measured by the ancestry. 



Protective coloring. Any color effects which, by mimicry or otherwise, make 

 the animal less conspicuous. 



Protoplasm. Living matter in general. 



Pure breeding. Mating only registered animals together. Coming to be used 

 also in plant breeding. 



Pure bred. An animal or plant whose ancestry is registered on both sides. 



Recessive characters. See Characters, recessive. 



Reduction. The halving of the characteristic number of chromosomes dur- 

 ing the process of maturation. 



Registration. The filing for print with the officers of a breeding association 

 of the pedigree of a pure-bred animal. 



Regression. The tendency of individuals toward the mean of the race, 

 whether the immediate parentage be better or inferior to the average. 



Reversion. An instance in which the offspring resembles a remote ancestor 

 more closely than it does the immediate parent. 



Score card. A scale of points upon which breeds or individuals may be 

 assessed and judged, character by character and point by point. 



Scrub. An animal that has little or no pure blood in its ancestry. 



Selection. In general, the limiting of reproduction to certain favored indi- 

 viduals, either by nature or by man. 



Selection, methodical. The selective process as carried on by man in order 

 to accomplish changes especially desired by him. See Methodical selection. 



Selection, natural. The selective process as determined by the environment. 

 .See Natural selection. 



Spaying. The removal of the ovaries of the female, thus preventing 

 reproduction. 



Spermatozoon. The male sex cell among higher animals. Plural, spermatozoa. 



Sport. .See Mutant. 



Standard deviation. A mathematical measure of variability the same as 

 average deviation, except that the several deviations are squared in determin- 

 ing its value. See Average deviation. 



