276 GLOSSARY 



from a cross between two individuals possessing respectively 

 the two characters of a MendeHan pair. 



Duplex eyes are those which have a layer of brown pigment in 

 front of the iris {See Iris). 



" Extracted " is the term applied to the individuals, in the 

 second hybrid generation from a cross, which resemble the 

 parent forms that were mated to make the cross. An 

 " extracted " green is a green which appears in the second 

 or a subsequent hybrid generation from a cross between a 

 yellow and a green pea. 



Fi, a symbol, introduced by Mr. Bateson, as an abbreviation 

 for the first hybrid generation. 



F2, a symbol for the second hybrid generation. 



F3, a symbol for the third hybrid generation. And so on. 



Factor, a name for the thing in a germ cell which makes that 

 germ cell develop a particular character, such as tallness 

 as opposed to dwarfness. 



Fasciated plants are those in which the nodes do not, as in the 

 normal plant, succeed one another regularly up the stem, 

 but occur in profusion at the top. 



Gamete, a name for the reproductive cell, whether male or 

 female, in both animals and plants. 



Germ cell, the equivalent of Gamete. 



Heterozygote, a zygote (q.v.) resulting from the union of two 

 gametes bearing dissimilar factors — one a dominant, the 

 other a recessive one. DR is the symbol for heter- 

 ozygote. 



Homozygote, a zygote (q.v.) resulting from the union of two 

 gametes bearing similar factors, which may be either both 

 dominant, producing a dominant homozygote or DD, or 

 both recessive, producing a recessive homozygote or RR. 



Internode, the section of the stem of a plant between two nodes. 



