126 POULTRY CULTURE 



This principle of gametic segregation and the modes of its 

 action in the breeding pen I have endeavored to point out in 

 the tabulated list. 



Each group of symbols represents a number of characteris- 

 tics, sometimes containing both units of pairs of character- 

 istics, e.g., WbRs represents that the fowl in question has the 

 gametes for white plumage and black plumage, for rose-comb 

 and single-comb, and possesses them in equal numbers. 



In the sperm-cell or egg-cell which it imparts it may give 

 off a gamete representing white plumage (W) or a gamete 

 representing black plumage (b), but not both at the same time, 

 i.e., not a gamete representing half white and half black. 

 The gametes are distinct units. They are segregated, i.e., 

 divided, separated, one from the other. What is true of 

 color applies in the same way to the comb, and also to other 

 Mendelian characteristics, if present. As an illustration, it 

 may be said that they lie side by side like the numerous 

 sections or "quarters" in an orange, each contained in its 

 own envelope, while the cell-like fruit within the segment 

 may represent as many distinct units of many pairs, but not 

 the two distinct characteristics of any pair. 



How this segregation of the gametes, which represent the 

 dominant and recessive characters, takes place in the or- 

 ganism is at present unknown, though it is not impossible 

 that the further studies and researches of embryologists may 

 discover it. 



What is important is the fact, proved by abundant experi- 

 ment, that these two "potential unit characters" do segregate, 

 and that the adult organism cannot have both. "Interme- 

 diate forms or blends do not occur in Mendelian phenomena." 



In describing the ratio of their transmission by hybrid 

 organisms, the expression "on the average" has to be used. 

 There is no proof that they are given off alternately, though 

 it is assumed that they are present in equal numbers. It is 

 not to be taken as proved that the group of sixteen inheritances 

 I have given will be present in the exact order in each sixteen 

 of the offspring, though if the number be multiplied by ten 

 it would be found that they would be very near the number 

 given. 



