618 UENKT1C8 IN RELATION TO AGRICULTURE 



has been derived from only one of the two generating gametes. Both eggs and sperms 

 produced by such an individual are typically of two kinds, half of them containing 

 the factor in question, the rest lacking this factor; consequently the offspring of hetero- 

 zygous individuals usually consist of a mixture of individuals some of which possess 

 the corresponding character while others lack it. 



Homosynapsis. As applied to the sex-chromosomes, the pairing of two X- or 

 two TF-chromosomes. 



Homozygosis. The state of being homozj'gous; the extent to which an individual 

 is homozygous. 



Homozygote. A homozygous individual. 



Homozygous. That condition of an individual in which any given genetic factor 

 is doubly present, due usually to the fact that the two gametes which gave rise to 

 this individual were alike with respect to the factor in question. Such an individual 

 having been formed by the union of like gametes, in turn generally produces gametes of 

 only one kind with respect to a given character, thus giving rise to offspring which are, in 

 this regard, like the parents ; in other words, homozygous individuals usually breed true. 



Hormone. A substance secreted or found in some organ or tissue and carried 

 thence in the blood to another organ or tissue which it stimulates to functional activity 

 or whose functions it inhibits. 



Hybrid. The offspring of animals or plants of different genotypes, varieties, 

 species, or genera. 



Hypertrophy. An enlargement of a part of the body from excessive growth or 

 multiplication of its elements. 



Indigenous. Native, not exotic. 



Inter se. Between or among themselves. 



Interference. Protection from coincident crossing-over of loci on either side of 

 the point of crossing-over. 



In utero. In the uterus or womb. 



Lethal. Destructive of life. 



Linkage. That type of inheritance in which the factors tend to remain together 

 in the general process of segregation; "gametic coupling" of the older terminology. 



Locus (pi. loci). A definite point or region in a chromosome at which is located 

 a genetic factor or gene. 



Lymantria. A genus of moths. 



Meiosis. See reduction or heterotypic division. 



Metabolism. The sum of the chemical changes within the body, or within any 

 single cell of the body, by which the protoplasm is either renewed or changed to per- 

 form special functions, or else disorganized and prepared for excretion. 



Mitosis. Indirect cell division, the characteristic method of multiplication of 

 somatic cells, in which each chromosome is halved longitudinally, one-half passing 

 to each daughter cell. 



Monoecious Plants. Those having both sexes in the same plant. 



Morphology. The branch of biology concerned with the outer form and internal 

 structure (without regard necessarily to the functions) of animals and plants. 



Multiple Allelomorphs. Factors occupying the same locus of homologous 

 chromosomes; the characters conditioned by such factors. 



Mutant. An individual of a genotypic character differing from that of its parent, 

 or those of its parents, and not derived from them by a normal process of segregation 

 or by crossing-over. 



Mutation. The result of a change in genotypic nature independently of normal 

 segregation or of crossing-over; strictly an alteration in the fundamental nature of a 

 genetic factor. 



