152 INHERITANCE, FERTILITY, AND SEX IN PIGEONS. 



male risoria (table 144); more fertile with a male hiimilis (table 145). Two 

 brother-and-sister matings of humilis-risoria hybrids are of interest. One pair 

 of hybrids which were themselves hatched from eggs laid toward the extremes 

 of the season (April and August) was very weakly fertile; only one of their eggs 

 hatched in about 18 tests (table 146). The other pair of parents, hatched from 

 eggs (same clutch) laid in June. This pair was much more fertile, hatching 11 

 young from 34 tests. One of the males of this group (Fj generation of humilis x 

 risoria) is shown in adult plumage and in juvenal plumage in pi. 23. These illus- 

 trations will show that there is a greater similarity of the Fj generation than of 

 the Fi generation, with the darker species (^7. humilis). The two dark birds of 

 this fraternity whose sex is known were males; the only light-colored bird whose 

 sex is known was a female. 



Is the whole series of developmental stages a series of reversions?'" If so, then a final 

 stage, which is a case of re^'ersion, must be arrested development. The matter is so regarded 

 by Ewart. I think reversions are not arrests, but due to germs of different stamps. Germs of 

 the same bird may be sometimes white, sometimes brown. My experiments in crossing, and 

 the issue of white offspring" from dark hybrid parents, seem very instructive in this sense. 



We do not start with like germs and stop short with one germ, at white for example, and 

 go on with the other to brown. Otherwise the latest stage would be preceded by white ; or, if 

 white be the later stage, then it should be preceded by brown, the brown appearing in the 

 first plumage, the white in the second, after the manner of the geopelias."- In this case it 

 is not a question of supremacy (prepotency) — a struggle for mastery as Ewart suggests — 

 with victory faUing now to the ancestors, now to the moderns, but it is a question of original 

 constitution. In the case of these geopelias the germ develops and at one age gives the 

 ancestral color and a Uttle later it gives the final color. (T 22) 



Table 141. 

 Pair 1. 

 & Humilis-risoria hyb. (K 2) : 3/9/01 ; reddish isabelline. 

 9 St. alba (O); 9/20/03; white. Purity (?). 



9 Al. 7/4/02 very light pale risoria dead 10/5/04* 27 mo. 



d' A 2. 7/6/02 very light pale risoria dead 11/27/02 4^ mo. 



9 B 1. 8/13 complexion dark dead 5/23/05 33| mo. 



cf B 2. 8/15 complexion dark dead 10/23/02 2 mo. 



9 C 1. 2/13/03 complexion dark '. (sick, killed); 4/15/05 2fimo. 



cf C2. 2/15/03 complexion dark (sick, killed) ; 7/21/04 17 mo. 



D 1. 3/27; not hatched. 



D2. 3/29 light risoria dead 4/29/03 1 mo. 



El. 5/4; deserted. 

 E 2. 5/6; deserted. 



c? F. 5/15 pale risoria, w. flush of red dead 12/10/04 19 mo. 



G 1. 7/7 risoria-humilis dead 9/26/03 2J mo. 



G2. 7/9 light risoria de.gd winter 1903-4 7 (?) mo. 



Pair S. 

 cf Risoria-humilis (A 1). 

 9 St. alba (1); (1901). Purity (?). 

 A 1.5/12/021 ,, , • , J u 11 n 1. 5/22; circle of blood. 



A 2. 5/14/02/°°^ ""*" '""'"■^°' °"'" P"''"''^ ''''' H 2. 5/24; no development. (DD 9) 



*This and the two following clutches present an interesting situation as regards longevity and sex on the one hand, and 

 egg of the clutch and sex on the other. Here the sire is a hybrid, the dam possibly a hybrid; the more typical relation of 

 the sexes within the clutch is reversed; the more typical longevity relation is maintained. — Editor. 



'» This is the most complete statement I find on the subject of reversion, and it has been thought best to place 

 it here. It was probably written about 1900-1, and apparently as a result of an examination of Ewart's (The Penycuik 

 Experiments, London, 1899) ideas on reversion. — Editor. 



"Something of the author's (earlier) idea of "germ differences" is thus included in the discussion of reversion. — 

 Editor. 



'-See Chapter X, Vol. I. — Editor. 



