BREWSTER’S WARBLER. 73 
P w (pinus) X p W (chrysoptera) 
| 
F, PwpW 
That is, the offspring of the first generation will all be impure dominants, 
but in plumage P W, lewcobronchialis. If two of these hybrids of the first gener- 
ation should mate together and produce offspring the second filial generation 
would comprise Brewster’s Warblers, Blue-wings, and Golden-wings, and also 
the pure recessive, Lawrence’s. Warbler (pw pw), in the relative numerical 
proportion of 9, 3, 3, 1. But we have seen that as far as observations show, 
Brewster’s Warbler always breeds back with one of the hypothetical parent 
forms, pinus and chrysoptera. In that case the advent of Lawrence’s Warbler 
will be deferred to the third filial generation when it will come to light in small 
numbers as compared with the dominant hybrid, Brewster’s Warbler. 
Pw xpW 
| 
pW xX PwpW xX Pw 
| | 
chryso. =pW pW Pw Pw =pinus 
leuco. =pW Pw PwpW =leuco. 
Fy, leuco. =pW PW : Pw PW =leuco. 
chryso. =pW pw + Pwpw =pinus 
Fy, leuco. = pW Pw X pW pw = chryso. 
| 
pW pW = chryso. 
pW pw = chryso. 
pW pw) = chryso. 
pW pW = chryso. 
PwpW_ = leuco. 
Pwpw = pinus 
F3 Pwpw = pinus 
PwpW = leuco. 
pw pW. = chryso. 
pw pw = lawrence 
pw pw = lawrencei 
pw pW = chryso. 
PW pW = leuco. 
PW pw = leuco. 
PW pw = leuco. 
PW pW = leuco. 
