57 TH.E AMERICAN NATURALIST [VOL. XLIX 



Heterozygosity. The condition of an organism due to the fact that it is 

 a heterozygote; the state of being heterozygous; the extent to which an 

 individual is heterozygous. 



Heterozygote. ' ' A Mendelian hybrid resulting from the fusion of two 

 gametes that bear different allelomorphs of the same character and which 

 in consequence does not breed true; contrasted with homozygote." 



Heterozygote. A zygotic individual in which any given genetic factor 

 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 gene in question, the rest lacking this gene; conse- 

 quently the offspring of heterozygotes usually consist of a mixture of indi- 

 viduals, some of which possess the corresponding character while others 

 lack it. 



Homozygosis. "Development from a zygote originating from a union 

 of two gametes of the same kind. ' ' 



Homozygosis. The state of being homozygous; the extent to which an 

 individual is homozygous. 



Homozygote. "A zygote formed by the conjugation of two gametes of 

 the same stock; any animal or plant that receives and retains the dominant 

 or recessive characters of both its parents, and is therefore said to be true 

 to type, and breeds true to type." 



Homozygote. 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 determiner, 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 the given 

 character, thus giving rise to offspring which are, in this regard, like 

 the parents; in other words, homozygotes usually "breed true." A 

 "positive" homozygote with respect to any character contains a pair of 

 determiners for that character, while a "negative" homozygote lacks this 

 pair of determiners. 



"Two gametes of the same stock'* is ambiguous because of the 

 indefiniteness of the word "stock." Many homozygotes receive 

 some dominant and some recessive characteristics of the two par- 

 ents ; and what can be intended by the statement that a plant or 

 animal which receives certain characteristics also "retains" 

 them? How could it do otherwise? 



Hypostasis. (Not given a genetic definition in the dictionary.) That 

 relation of a gene in which its usual reaction fails to appear because of the 

 masking or inhibitory effect of another gene; contrasted with " epistasis." 



The corresponding adjective ' ' hy postatic " is also not given a 

 genetic definition in the dictionary. 



Mendelize. "To cause to follow Mendel's law of inheritance." 

 Mendelize. To follow Mendel's law of inheritance". 



The word is rightly indicated in the dictionary, as an intran- 

 sitive verb ; it is manifestly incorrect to define it by the use of a 

 transitive verb. 



