314 DOMESTICATED ANIMALS AND PLANTS 



Grading. Breeding scrub or unpedigreed stock to registered males. 



Heredity. The transmission of racial characters from ancestry to offspring. 



Hybrid. The offspring of hybridization, carrying the blood of two or more 

 species or races. 



Hybridizing. That kind of crossing in which the male and female are of 

 different species or of distinctly different races. 



Id. A term used by Weismann to denote an orderly and definite association 

 of biopheres operating together towards the determination of a definite 

 character. 



Latent characters. See Characters, latent. 



Mammals. Certain species of higher animals in which the fertilized ovum is 

 retained and embryonic development takes place inside the body of the mother 

 until birth ; specifically, those species which suckle the young. 



Maturation. The final stages of division in sex cells just before attaining the 

 conditions suitable for fertilization. 



Mean. The average. 



Mendel's law. The law which states the way in which racial characters will 

 be distributed among the offspring of hybrid parents. 



Methodical selection. The imitation by man of the operation of natural selec- 

 tion as he attempts to secure the favorable development of especially desirable 

 characters in domesticated animals and plants. 



Mimicry. The resemblance of one species to another or to some natural 

 object in such a way as to be protective against possible enemies. 



Mitosis. The process of cell division in ordinary growth. See also 

 Maturation. 



Mode. The most common or typical value of a racial character. 



Mutant. An individual or strain essentially new and produced spontaneously 

 by nature through crossing, bud variation, or otherwise ; synonymous with the 

 older term " sport." 



Mutation. The production of mutants or sports, which see. 



Natural selection. The oppressive effect of the environment by which many 

 individuals are unable to endure, and which therefore operates to destroy a 

 large proportion of the race. Those which are able to endure the hard fea- 

 tures of the environment not only survive, but, prospering by other conditions, 

 are said to be selected in this natural way. 



Nucleus. That part of the cell which contains the chromosomes, which 

 takes the lead in cell division, and which seems normally to be equally divided 

 between the daughter cells, whether in ordinary growth or in maturation. 



Ovary. The organ in which the ova or female reproductive cells develop. 



Oviporous. Said of species which lay eggs in which, like birds, the em- 

 bryonic development takes place outside the body of the mother by the 

 process of hatching. 



Ovule. The female sex cell of the higher plants, which, upon fertilization by 

 the pollen cell, is capable of developing into a new plant. 



