ta womatens hire eae : hate 3 Reet pene son eek rey ae cick ee warren BOCA Sceeer ys rire nears eT eee ee eee eee BON ES ee BOO SNe Cadet Ewe tee AD OOS PU ES wees? 06 Oe Saiuyvudly INSTITUTION INSTITUTION INSTITUTION INSTITUTION NOILALILSNI. NVINOSHLINS S31YWVYSIT_ LIBRARIES SMITHSONIAN INS’ NVINOSHLINS S3IYVYSIT Y “ee NVINOSHLINS S31uvUaIT SMITHSONIAN NVINOSHLIWS SMITHSONIAN SMITHSONIAN SMITHSONIAN LIBRARIES SMITHSONIAN _INSTITUTION NOILNLILSN LIWS SaIYvudII NVINOSHLINS $3 3 2 0 eS g yey : KE 24 \ z “Gs : WK =f Ss =! “iG ree] NS & x fo} Z = an 4 =i) nx NIAN INSTITUTION NOILNLILSNI NVINOSHLINS S3!IYVYdGIT LIBRARIES SMITHSONIAN INS] SAaINVUGIT LIBRARIES INSTITUTION NOILALILSNI INSTITUTION. NOILMLILSNI Sa14VYAIT LIBRARIES INSTITUTION sadiuvygi INS SSIYVYEIT LIBRARIES ‘. SMITHSONIAN INSTITUTION NOILNLILSNI NVINOSHLINS S3I x Sy NVINOSHLINS S3INVYSIT_LIBRARIE Y Ry NVINOSHLIWS »~ NIAN INSTITUTION NOILNLILSNI_NVINOSHLINS S3IYVYaIT LIBRARIES SMITHSONIAN _INS1 NVINOSHLIINS \ SS SMITHSONIAN 4 SMITHSONIAN ; KE 4z jo NVINOSHLIWS SMITHSONIAN Z_* : ZW. & : g p43 : 2 NY: Z 2 fz Nae é 2 NOG = = S (e) Ba (2) “SS S fo) = fo} Zz ay a - =z a Zz LINS S3INYVYdIT LIBRARIES SMITHSONIAN INSTITUTION NOILNLILSNI NVINOSHLINS S31 = cr z fir =z La oy z 9° o 2 “oO ° a SS ce) > - So) = eo] Les? ee] WAG e R02 > 2s > = EX = y 5 - b S 5 F & Sue a Zz as Z m 8 INIAN INSTITUTION NOILALILSNI NVINOSHLINS S31YVYaiI_LIBRARIES. SMITHSONIAN _INS z << 2 z g z Ko z z = SS i si . re VSS = > AS ENN F 3 2 ff te 502 i z < EVN 2 = BGde BRR 8 2 => 2 = 2 “yp = SS Zz =. a 2 a z = . 2 A WINS Salyvugi7 LIBRARIES SMITHSONIAN INSTITUTION NOILNLILSNI NVINOSHLINS S31 ~ ul lu ty re iJ \ - « Uy 5 : SN ey 2 5 a W 3% a » 2 rl 2 = z as 2 Nee NIAN INSTITUTION | NOILALILSNINVINOSHLINS (S31uvudi7 LIBRARIES_ SMITHSONIAN INS Ly, = ‘S) STU = i . S) = 29'NG o “ oa Ly, Ea Ny We i 2 en = Ly, 2 E GA 2 GE 33> ae Se Jie ZHRe El LIBRARIES SMITHSONIAN LIBRARIES SMITHSONIAN = 7) ; Ss rahe 4 eee Zo : “yy ) a yi = a ~NOILALILSNI NVINOSHLIWS 2 o mf =e] a > = es) p m = wn LIBRARIES SMITHSONIAN z o c z r 4 > =x e 6 : Zz = > 7) 2 NOILNLILSNI_ NVINOSHLIWS 2) ja J n ; = 4 c ie 2 S Wi a = ~\ ; 2 ‘LIBRARIES ea ESONIAN : 0 5. a Ey 9) E % = (2) P Zz NOILNLILSNI INVINUOPLIIND eh" je SMITHSONIAN LIBRARIES SMITHSONIAN RIES LIBR FITUTION NOILNLILSNI NOILNLILSNINVINOSHLIWS EEUTIVUIN NUTLTILILZONI “| uvuydgl INSTITUTION NOILNLILSNI INSTITUTION NOILNLILSNI NVINOSHLINS ~ za io — (ey = c 2° a ° = ie) : 5 “ff fF 2 5 2 = > my Mae = E a E : i cA = F 2 = f ye ae ae Z rs Z “NOILALILSNI NVINOSHLINS S31YVYSIT_ LIBRARIES SMITHSONIAN n we 2) = Roe ” Sy ap = = AS = 5 ae 4 z WS . bes ; 8 ae BRC 2 > a5) O 4 <= \. (eo) 3 = = 5 pis ; a 2 5 . 3 INSTITUTION NOILOALILSNI NVINOSHLIWS LIBRARIES x Saiuyvudii LIBRARIES SMITHSONIAN INSTITUTION NOLLNLILSNI SAINVYGIT LIBRARIES SMITHSONIAN SaSiyvudil INSTITUTION SMITHSONIAN NVINOSHLIWS S3IYVYEIT LIBRARIES SMITHSONIAN INSTITUTION ES SMITHSONIAN ii NVINOSHLIWS NOILNLILSNI LIBRARIES INSTITUTION NOILALILSNI NVINOSHLIINS INSTITUTION NOILNLILSNI INSTITUTION LIBRARIES, SMITHSONIAN NVINOSHLINS S31yvud!T NVINOSHLIWS SMITHSONIAN Ze. he 7 SMITHSONIAN INSTITUTION NOILALILSNI NVINOSHLIWS Z Ko Ss LIBRARIES DONG S f= 4 a SI PPR Saluyvugiy YVUYdIT LIBRARIES ITUTION NOILNLILSNI UVYdIT LIBRARIES Wash’ NOILNLILSNI NVINOSHLINS S3tuyvVuUaIT_LIBRA SAJIYVeRgIT_LIBRA NOILN1 YY wz bl saruvugi7_LiBRA NVINOSHLINS S31y¥vyualt INSTITUTION _ NOILNL INSTITUTION NOILNLILSN ° ‘ NOILAL y fii} LIBRARIES SMITHSONIAN saluvudi7 LIBRA o a > za m uw INSTITUTION NOILNI SK = AS ey = WAS, N WN z Ny > GQ x me cj saruvugi7_LIBRA = w =! ae | = al (e) za INSTITUTION _ NOILM 2) Ke =) = INHERITANCE IN POULTRY BY C, B. DAVENPORT DIRECTOR OF STATION FOR EXPERIMENTAL EVOLUTION, COLD SPRING HARBOR, NEW YORK WASHINGTON, D. C. Published by the Carnegie Institution of Washington 1906 "INHERITANCE IN POULTRY BY C. B/ DAVENPORT DIRECTOR OF STATION FOR EXPERIMENTAL EVOLUTION, COLD SPRING HARBOR, NEW YORK WASHINGTON, D. C. Published by the Carnegie Institution of Washington 1906 PUBLICATIONS OF THE CARNEGIE INSTITUTION OF WASHINGTON, No. 52 PAPERS OF THE STATION FOR EXPERIMENTAL EVOLUTION, No. 7 PRESS OF JUDD & DETWEILER, INC. WASHINGTON, D. C. OD > . Statement of Problem.. . Method and Material . Results of Crossing... TABLE OF CONTENTS. Series I. Silesan Black Minorca arm White-crested Black Polish...........005 ..0 Statement of Problem...... The Racesas a Whole Table of Characteristics Remarks on the Characteristi bets 1, Comb, 7; 2. Nostrils, 7; 3. Form of Skull, 8; 4. Crest, 9; 5. Color of Crest, 10, IVEel tes tel oetrn corse seuss eascneaseesstrerasenccectcrers PRIEST tS senaancecsvorresasaanccserecarserenasncccsaceseass 1, Comb, 10; 2. Nostrils, 12; 3. Cerebral Hernia, 13; 4. Crest, 14; 5. Color of Topof Head, 15 ; 6. Correlation of Characters, 16, ISON CLUSIOMSereesccrvrcaceacensersesccnesavacdccaesscns Series II. Single-comb White Leghorn and EV OUC ati erencessnccessnnesecescentesscossceneencleevestacrss The Races asa Whole Table of Characteristics..... Discussion of Characteristics 1. General Plumage Color, 1 2. Color of Upper Mandible, 19 ; 3. Nostrils, 19; 4. Comb, 19; 5. Whiskers or Muff, 20; 6. Beard, 20; 7, 8. Crest; Cere- bral Hernia, 20; 9. Foot Color, 20; 10. Number of ‘ues, 20. Previous Investigations Material 0 RESUS ececce cocccessesconverssscccss ageoommecdedod 3 | WOKiannosseoos Present ..... Normalieniaerrcre ene eee ° VAP llowne aencios Present |MExtraseeieee les oe I | Usbrant oagagone Absent eNormialliecil| WAnIteR eer yetterierterls I | 2E6%5)8 Co ogecbapol Absent . Normal | Black and white. . I | 1ebF Ad ooosonc00 | -Albsent) <2) | PETS soc gllpaooouds0ns 946000650 ° (li) SRF og goo onc | Present ..... |i caves uacgenctres Wh seevscovarciste raisaske ere tool Ssare % 0 (alWowercnee cnc | Absent ..... | Normal aWihlitele sentence 6 | Low Absent Normal....| Black and white..... fo) | WOWerreen steer Absent...... | Extra HALPER OR ncee Comenel| 3) WW OWpetelerreeterciers Absent..... 15>-46¢,e np oo Black and white ° | diieYeud soe coo Presents ysjeen Normal ier eteletereitiertetiiet rents 2 | | eesoobocacos leeresent rere |) ERR ocodallsooud doonsednonsudoD 0 Ishtas\ooanouese Absent...... Nyse olaanopsnaposoosBUoMoRé ° | pEieheeeee Absent...... |) deoxetiral eh cieyell cteepscevolianere stakes coments o Isha Gcoscooun Present lelslele | Nherselle sc ollaogonaccdsec0nnKe ° [Li 2sbhaele ASeoodos Present ..... | Eixtrascn RAB eacaaisacira met arc oO (Ul owsretecltertets: | PAlbsents-155- Normal AWM Godconaeoea coe ° | DOW eleietereisteyerete | Absent...... Normal | Black and white..... ° GON? weaeacaur Aibsentiervateys Extra...... I Bvceeararcnre ooetatelonsteleyonerare fo) | TOW vetet lai | Present ..... [aN Giant Wezalleehogosntageo: posoase I MG OMierreisiteolers Rresentryrciac extra evel eictiololteteacanciieier terete fo) Seo) ul Teta eh oogoas Npsentae ent Normal l-WWiahitebn cnncmnene 4 | I) weetlstscggoooas Absent...... Normal | Black and white..... I | ISG Ratko en daos Absent..... Hixtral jie NBAN ALLL Aeene Aamir 3 IsbTecdoaaaee Absent...... Extra nele | Black and white..... I | 18 Stn conab5oen Present\i2.... Normale eWihitesepeeeeee pee 3 Jetta’ gouauoso|| Present .... | Normal | Black and white..... I ett) Veeeaasce | Present .....| Extra...... RPE isl Pein Pe a a fe) | oe | | 38 *Fig. 14. CONCLUSIONS. In the series of crosses between the White Leghorn and Houdan, Mendelian results were obtained as in the first series. Dominance, however, is frequently imperfect. The plumage color of the offspring of a pure homogametous white- and-black and a white arerarely pure white. Likewise in the second hybrid generation impure whites occur. Also, nostril-height exhibits imperfect dominance of the narrow type. The muff, beard, and crest, though always present in the first hybrid generation, are apparently always reduced. ‘The cerebral hernia, though recessive, affects the dominant normal skull. A heterozygous form results from hybridizing the single and V-shaped comb. The cleft comb is a neomorph, of which more will be said in the sequel (page 65). Polydactylism does not readily fall into the Mendelian formula. results, although suggestive, need support from other experiments. Hurst’s HOUDAN AND SINGLE-COMB BLACK MINORCA. 27 Few characters are correlated ; the second hybrid generation exhibits all combinations, except that high nostril and single comb do not occur together here any more than they do in the Minorca-Polish hybrids. Among heterozygous individuals, with Y-shaped comb, the combination of dominant characteristics (narrow nostril, no hernia, and white plumage) is the commonest, forming nine-thirteenths of all. These are also, apart from the Y-comb, all Leghorn characteristics. It appears, too, with the given parentage, that zovma/ toes are usually present. The low nostril and cerebral hernia combination occurs several times with or without extra toe. The combination refutes the notion of Wright (quoted at page 8) that there is any necessary relation between cerebral hernia and ‘‘cavernous’’ nostril. A high nostril was in two instances (both of which died very young, one before hatching) associated with a Y-comb, but it is doubtful if the median portion would have developed. The single comb may occur associated with a hernia (¢. g., No. 443, fig. 14), with extra toes and with mottled plumage, but in my records so far it is never associated with a high nostril. The V-shaped comb is commonly associated with high nostril, but rarely with a low one, despite the fact that low nostril is dominant. It occurs on white individuals thrice as frequently as on black-and-white ones; it shows no preference for the extra toe. The hernia is never found dissociated from the crest ; but the crest occurs three times as often as the hernia. Series II],—Houdan and Single-comb Black Minorca, STATEMENT OF PROBLEM. This series was undertaken to compare the behavior of the Houdan with that of the Polish (Series I, page 6) when crossed with the Minorca. THE RACES AS A WHOLE. The Houdan is deseribed at page 18 and the Black Minorca at page 6. Both of the races are fundamental and old. The Houdan contains the larger assemblage of new characteristics. TABLE OF CHARACTERISTICS. | | +4: | Discussed | Single-comb Black | Discussed Characteristic. | Houdan. at page— Saree | at page— 1. General plumage color..| Black and white. . 19 (princtueae. tan 29 2A COMP OLtMenesieereriiests Vidwies opsenotoor 19 antes AbeDd beOS hod if BeeNostril’form'= asec: | IWAGEU = Sere sisiacrecel| 19 Narrow.. .. .. 7 Aaa Srestrytiretcnlonacyereree WePresentanreiyc ue 20 A\DSeTitieray eves ieter | 5. Cerebral hernia........ pr tescrityrersaviaele 20 JADE is gaadoewr ObpMi nih fervaryerciaes colctorolcters ebresenteme ere. 19 Albsentiyenece ci. Go dkeaktelnadaaoauosco0dcoc eexesenta rues fret 20 INTIS, Gagccocod 8. Foot color....... opal VALLES crs revetneversate 20 Blackerrtmetceyers 29 mm Loeslerene veterans Pel etc uano itor 20 Am AW fai retetet tei cielo 28 INHERITANCE IN POULTRY. MATERIAL, As mothers, Nos. 8 and 11 (page 21), original Houdan stock, and later their daughters, Nos. 60 and 81, were used. No trap nests were employed in this series and consequently mothers are not exactly known. Father: No. 27, bred at the station, August, 1904, son of No. 12, Minorca cock (page 6) and a Minorca hen. RESULTS. 1. GENERAL PLUMAGE CoLor.—The young hybrids, like the young black Minorcas, contain much white on the belly ani primaries. In later molt- ings the white is replaced by black, but even at five months the primaries are sometimes mealy or white-spangled. Except for this the hybrids have lost the Houdan white and are of the Minorca color. Minorca uniform black is dominant over the Houdan mottling. 2. Comp.—Firsthybrid generation, Of 20 offspring 18 have a Y-shaped comb like the hybrids of Polish and Minorcas. In two cases (of egg embryos) the comb was recorded as single, but this is probably only the limiting condi- tion of the Y-shaped comb, which is here also the heterozygous form. 3. NostriL Form.—First hybrid generation. In no case does the nostril width exceed one-half. As in Series I and II, there is imperfect dominance of the narrow form. However, the nostril in this cross runs lower than in the Leghorn x Houdan cross. 4. Crest.—This is present in all first hybrids reared to a sufficient age to render an opinion possible. 5. CEREBRAL HERNIA.—F,. Always absent. Oneegg embryo, which died at about 17 days of incubation, had a vesicle protruding, uncovered by skin, from the top of the head at the usual position of the hernia. Sucha teretological case is not uncommon in straight bred Houdans. It is note- worthy to find it here where the cerebral hernia is recessive. 6, 7. MuFF AND BEARD.—F,. Present in all older hybrids. 8. Foot CoLror.—F,. Always black as in the Minorca. g. Tors.—Of 21 hybrids, 12 have 5-5 toes, 3 have 5-4 toes, and 6 have 4-4 toes. The proportion without extra toes is higher than in the Leghorn x Houdan first cross, being there 16.2 per cent, here 28.6 per cent. CONCLUSIONS. The following characteristics apparently exhibit alternative inheritance: Plumage color, nostril form, crest, cerebral hernia, muff and beard, leg color, and number of toes. Dominant are: Uniform black plumage color (imperfect), narrow nostril (imperfect), crest (imperfect), cerebral hernia (imperfect), muff and beard (imperfect), and black leg color. Of these the crest, muffling, and black leg color are positive characters in de Vries’ sense and are dominant. The color pattern of the Houdan yields here to black SINGLE-COMB LEGHORN AND ROSK-COMB MINORCA. 29 as it does in Series II to white; mottling is recessive to solid color. The comb, crest, muffling, and extra toe are inherited essentially as in Series II. Striking is the nearly universal imperfection of dominance. Series IV.—Single-comb White Leghorn and Rose-comb Black Minorca. STATEMENT OF PROBLEM. This cross was undertaken to learn the inheritance in these races of the characteristics described below. THE RACES AS A WHOLE. The Leghorn has been described at page 18 ; the Minorca at page 6. TABLE OF CHARACTERISTICS. Single-comb | Discussed) Rose-comb Discussed | ae | No. | Characteristic: | White Leghorn. | at page— | Black Minorca. | at page— | le 3 = | | | 1 | General plumage color. I Wikkitess char cc | 19 Black eseiee | 29 D || Carly sews soscooosve Singlet seco: 19 Rosettes 29 B | Foot Colors, «1. .- sees WellOwietrses- + «re | 20 | Blue-black.... 2 | | | REMARKS ON THE CHARACTERISTICS. 1. GENERAL PLUMAGE CoLor.—Black is one of the constituents of the color of Gallus bankiva, being the chief color of the breast. Just how a wholly black condition of plumage was attained is of course not exactly known ; there are, however, many instances known of melanic sports among birds. It is probable that wholly black varieties have arisen as a result of excessive production of the black pigment, melanin. 2. Comp Form.—The rose comb isa broad mass of erectile tissue replacing the single comb. Anteriorly it overhangs the nostrils and extends over and back of the eyes. The upper surface is covered by numerous tubercles. These do not, in young birds and females, run wholly at random but tend to lie in five or more parallel lines. Posteriorly the rose comb ends in a finger- like process or spike. The rose comb is the last term of the series starting at the single comb and having the triple or pea comb for its middle term. 3. Foor Cotor.—The dense black color of the scutes of the foot of the Minorca constitutes a positive or additive characteristic as contrasted with the pigmentless condition of the yellow-footed White Leghorn. MATERIAL. As mothers three White Leghorns were used, of unknown ancestry but reputed pure. They had fair Leghorn points except as noted in the descrip- tions given below. When mated with White Leghorn 13 ¢ they produced only white offspring. 10A. Feathers all white ; comb strictly single. 30 INHERITANCE IN POULTRY. r1A. Feathers mostly white, but some are sooty. The single comb is cleft behind for about one-fourth of its total length. 12A. Feathers all white ; comb strictly single. The father, No. 9A, also of unknown parentage, has a large rose comb go mm. long by 44 mm. broad at its widest part. The tubercles are very irregular, but five rows of them can be discerned. The plumage is prevail- ingly black, but many feathers of the back are tipped with white and several primaries are almost or quite white. RESULTS. This series of experiments has been carried as yet through only the first hybrid generation. 1. PLUMAGE CoL_or.—Highty-three first hybrids were obtained of ‘which 74 were white, either pure or with some black feathers, and 9 were deeply pig- mented. Females A and C yielded only white offspring. Female B, on the other hand, produced chiefly dark birds, recorded as ‘‘blue’’ or ‘‘ black- and-white.’’ She was the mother of the 9 pigmented birds just mentioned. B’s germ cells are probably mixed. The only two of B’s offspring reared to maturity are blue like the so-called ‘‘Andalusian breed”’ (fig. 54, pl. xvmz). Now blue is a combination of black and white and is a ‘‘ heterozygous form.’’ If blue birds, one of which is male, the other female, breed together, both pure black and impure white, as well as blues again, are to be expected in the proportions of 1:1:2 respectively.** Of the white offspring of both A and C it is noteworthy that the males are mostly pure white (7. ¢., without trace of black, although often suffused with yellow), while the females are always specked with black. 2. Comp Form.—Of 8o first hybrids 40 have single comb and 40 rose comb. This result indicates first that the cock is a heterozygote and consequently produces in its germ glands two kinds of germ cells, viz, those with the single- comb and those with the rose-comb determinants and second, that rose comb is dominant. Then: R single X DR rose gives 50 per cent DR rose and 50 per cent RR single. Bateson and Saunders (1902, pp. 102, 103) find rose comb of Wyandotte or White Dorking dominant over single comb of the Leghorn. Hurst (1905, p. 134) crossed a White Leghorn with a Black Hamburgh (rose comb) * Tegetmeier (1867, p. 185) states that blue Polish bred together throw cuckoo, white or speckled produce. Wright (1902, pp. 399-401) states that ‘Andalusians ’’ constantly throw black and also white chicks. Blue chicks are frequently produced by crossing black and white. Wright (1902) mentions such a result from crossing black and white Langshans (p. 291) and Wyandottes (p. 318). Such blues also throw whites and blacks. Inher- itance of blue is discussed by Bateson and Saunders (1902, pp. 131-132) and by Bateson and Punnett (1905, pp. 118-119). In the latter paper it is stated that of 75 offspring of Andalusians 17 were ‘‘ white splashed, 36 blues, 22 blacks.’? A blue bred to a white pro- duced 34 blue and 20 white splashed ; bred to a black it gave 27 blue and 19 black. SINGLE-COMB MINORCA AND DARK BRAHMA. By and got rose combs in all of the offspring. Here, too, rose comb is domi- nant over single comb. Rose comb is a positive variation. It behaves in Mendelian fashion. Although a neomorph, it is dominant. 3. Foor Cotor.—Excluding from consideration all but the older hybrids, 40 showed foot coloring as follows : Blackwblaishs willows Ore Sreenis cierereyjelelotelerlsiclelorNelsiviesater=vislrfohe) a) el 9 Wath sasnonsnnooboobo0s sataqou Rodos gudanooDDDDpODSUsOuDO DDoS 7 PANO? onooon daghuoaochAnnooonps oodndmoga4onoonn sooDGaDad OCOD 2 ADCOS CU Anits eet On GER CE CORRE ISIOIG OI ICROLIRIC DCR CER RR CRA a a PO IO OCMC ie This result indicates that one of the parents (probably the male) is a heterozygote containing traces of some white-legged ancestor. Yellow appears to be dominant over white and black, but to be imperfectly so. The black x yellow gives green or willow; the whitened yellow is ‘‘ white.”’ Hurst (1905, p. 137) finds that when blue-footed and yellow footed individ- uals are crossed, the offspring have light-blue feet. Yellow is in his case recessive. CONCLUSIONS. In general, plumage color, foot color, and comb form are inherited in Mendelian fashion. White plumage is dominant, although imperfectly so ; wherefore we have spotted whites and even blues. Rose comb is dominant ; whether perfectly so can not be determined until later. Yellow foot color seems to be dominant, but is imperfectly so, even the yellow legs showing traces of black. Series V.—Single-comb Black Minorca and Dark Brahma, STATEMENT OF PROBLEM. This cross was made to see the result of uniting two races as unlike as possible in origin and general form. THE RACES AS A WHOLE. ‘The Minorcas have been already described at page 6. The Dark Brahma race was originally imported from India near the home of Gallus bankiva ; yet it differs from it as much as does the Minorca. It isa blocky, short, stout-legged bird, is fluffy in plumage, and has a small pea comb and small wattles. It is, moreover, sexually dimorphic. The male (fig. 19, pl. v) has much more black in its plumage and is very differently marked from the penciled or barred female (fig. 18). The Dark Brahma has so many characters unlike those of the Jungle fowl that it is now thought to be chiefly derived from a different ancestor, namely, that of the Aseel and Indian races. 32 INHERITANCE IN POULTRY. TABLE OF CHARACTERISTICS. = ogs Single-comb No. Characteristic. Bla ae Minores. Dark Brahma. I Generalicolorneee ms aiiieciciors Black in both sexes..| Complex black, red and white pattern; sexes dissimilar. 2 | Wing coverts (wing bar)........ Blackie fantsecveeieceee Black, white, and red. Q | Cerys popat cooosacnoboooBOnonS SFA pon gessqeAcoe Pea. 4 Haxzlobpeicolorenececceiccietciste White, red mottling.| Red. IS RTS (COLO stayels}ateisce cle ovolerestoboieeialeke BLOWS ricyelsictorerversels Yellow. 6 | Foot and beak color.......... | Blue-black... ..... | Yellow. 7 Boot feathering... «0 -issiesie ore AtDSentincrictecineisiieiers Present and heavy. 8 Vulture hock.. . Sow obouae IAIDSEN Gree wrteotacercee Present. Gj) Wits Conoco ceeasogood Gogo Black. 20 jean Black, white, and red. REMARKS ON THE CHARACTERISTICS. 1. GENERAL, PLUMAGE CoLor.—The adult Minorca has a completely glossy black plumage. In the chick of two weeks the whole ventral surface is covered with a white down, and certain of the primaries, especially those at the distal end of the series, are partly or wholly white. The coverts over- lying these reminges are usually white also. The white on the wing grad- ually disappears in successive molts. The adult Dark Brahma has a sexual dimorphism of color. The female (fig. 18) is nearly uniformly penciled black and straw color. ‘The hackles have a broad whitish margin and the inner half of the vane is solid black. The male (fig. 19) has solid glossy greenish-black feathers in the tail, white feathers on top of the head, in the middle of the back and upper wing coverts; below black. Feathers with narrow black central stripe and broad white margin (lacing) constitute nape, hackle, and saddle. Red occurs on wing bar and humeral patch. In the down plumage Brahmas of both sexes are longitudinally striped buff and black. 2. WiNnG BArs.—The wing bar of the male Dark Brahma depends upon the fact that the wing coverts of the second and third rows (which are black at the base) have a white tip and a transverse band of red in the middle between black and white. Inthe higher coverts and on the shoulder the red still occurs, but it is reduced in extent. 3. Comp.—The single comb is found on Gallus bankiva and has sometimes been regarded as the only ancestral form. The pea comb is a distinct type, consisting of a median comb bordered on each side by an accessory comb. The origin of the pea comb is obscure but certainly ancient. Wright (1902, PP. 265, 33°, 339) contends that it arose in the Aseel, a type of oriental fowl regarded as the ancestor of the Malays and Indian Games and believed not to have originated from Gallus bankiva, but to represent a distinct species. According to this view the pea comb has not arisen from the single, but is coordinate with it and of equal age. From the ancestral breed it has become SINGLE-COMB MINORCA AND DARK BRAHMA. 33 fixed upon others. Although not typical of the Malay breed (which has a small ‘‘ walnut’’ comb), it often appears when two walnut combs are bred together.* The pea comb is found also in certain derived races, particu- larly in the Brahma, and from this it has been engrafted on various other breeds, notably on the Plymouth Rock of America and on the so-called ““Buckeyes.’’ + 4. EARLOBE COLOR.—Two main color types of earlobes are found in poul- try, red and white. The former occurs in the Jungle fowl, Aseels, Indian Games, Javas, Dorkings, Cochins, Brahmas, and other foundation stock ; con- sequently it must be regarded as the more primitive. The white earlobe seems to have arisen in the Mediterranean type. It finds its highest expres- sion in the White-faced Black Spanish. It has become a constituent of the Houdans and La Fléche among the French breeds and of the Hamburghs. 5. Irts Color.—Among poultry this ranges from a gray or pearl through yellow to orange, red and bright red on the one hand, or through a dirty red or bay to brown and black on the other. The red type seems to belong to the descendants of the Jungle fowl; it is found in the Jungle fowl, in most Games, in most Mediterranean breeds, in most French fowl, in the Dorkings, and in many of theirderivatives. The lighter colors, yellow and pearl, are found in the Aseels, Malays, Indian Games, often in the Brahmas, attesting their origin from the Aseel group, also in many Cochins, where it is said to be ‘‘ very hereditary ’’’ (Wright, 1902, p. 320). The dark colors— hazel, brown, and black—are found in certain Game fowl of dark plumage, the Brown-Red Games, the Birchen Games and the Black Sumatras. They are found also in the Black Javas of America, in the Langshans, and sometimes the Orpingtons. Both the Langshans and Orpingtons have derived their eye color from the Java. Dark-brown eyes are found among the Mediter- ranean fowl only in the Black Minorca which we have to do with here. Whence acquired by the Minorca is uncertain ; possibly indirectly from the Java. Finally, a perfectly black iris is found in the Silkies, where it is probably due to the melanic sport that has made also skin and connective tissue black. 6. Foot CoLor.—This varies with the general skin color. ‘The primitive color of the Gallus bankiva group is an olive, commonly called ‘‘ willow.’’ This is found in ordinary Game fowl. The Aseel-Malay-Indian type has yellow feet. To this type belong the yellow feet of the Brahma and the Cochin and doubtless also of the American Dominiques, which have trans- mitted it to the Plymouth Rocks and Wyandottes. Finally, the Leghorns have bright yellow feet. By increase of the black pigment in certain birds of dark plumage there have been produced from the willow foot the blue, blue-black, and leaden blue * Wright, 1902, p. 325. + American Standard of Perfection, 1905, p. 79. 34 INHERITANCE IN POULTRY. feet of numerous races, e. g., Black Cochins, Black Wyandottes, Black Java, Black Leghorn, Black Minorca, White-faced Black Spanish, Hamburgh, the French fowl, black and dark-colored Games, and the Silky. By decrease of pigment are derived the white feet of the Dorkings and Houdans. ‘This loss of pigment may be regarded as a mutation. It is associated with red or yellow eyes. Considering the Aseel type and the dankiva type as specifically distinct, the cross of the yellow foot and the blue-black foot in the present series is a cross between specific characteristics. 7. Foor FEATHERING.—In Gallus bankiva and in the Aseel-Malay group the feet are without boots. The same is true of the Game fowl, although minute feathers are sometimes found on their feet. Foot feathering is found among various species of birds; among scratching birds, in grouse, ptarmigans ( Zetreo, Bruasia, Lagopus), among some pigeons, and the owls. Typically absent from the Gallinze, it has cropped out in the Brahma, Cochin, and, probably independently, in the Silky and Sultan. In these groups it has been preserved because of its importance in brooding or because it has struck the fancier’s eye. 8. VuLTURE Hock.—This consists of long stiff quill feathers projecting backward at the heel joint. It is found among poultry only in the Cochin- Brahma group and its derivatives. This characteristic is a good example of a progressive variation. MATERIAL. The cock used in this cross, No. 122 (fig. 19), was a bantam Dark Brahma, weighing 1,900 grams, received (February, 1905) from F. H. Hodges,* Red Bank, New Jersey, who is a successful breeder of this variety. The cock is typical of his kind. ‘The hens were four Single-comb Black Minorcas, Nos. 14 (fig. 3), 16, 18, and 28, of which the three former were purchased of Mr. George C. Ely in July, 1904, and No. 28 was hatched at the station in August, 1904, from one of the purchased hens mated with the full-blooded Minorca cock No. 12. RESULTS. Only the first generation of hybrids has been reared up to the time of writing. 1. GENERAL PLUMAGE CoLor.—Inall cases (41) the hybrids are prevail- ingly black. Usually the feathers of the occiput and nape are laced with white, much more in the males than in the females, and the hackles of the male are obscurely barred or splashed with white (fig. 21). Evidently the white lacing of the Dark Brahma is trying toassert itself. The color of the wing coverts is considered in the next paragraph. The down of the young * Foot marked ‘‘F. H. H., 164.’’ SINGLE-COMB MINORCA AND DARK BRAHMA,. 35 is dead-black, being without the longitudinal stripes of the Dark Brahma young, and, for the most part, without the white wing feathers and ventral aspect of the young Minorca. Nevertheless, exceptionally, one finds the chin and part of the throat of the young white, the head feathers may be tipped with white, and in one or two instances a little white occurs on the wing. The young plumage seeims to be a neomorph, but on the whole it belongs rather to the Minorca type than to the more primitive Game type of juvenile coloration. 2. Wine Coverts.—In 14 grown male hybrids of which I have records, a more or less prominent wing bar, formed by black, red, and straw-colored feathers in the third or fourth row of wing coverts, occurs (figs. 20, 21). The five females are wholly black, but even in these the wing coverts are barred with an iridescent purple black ; consequently a disturbance of the coloration of the wing coverts may be said to be typical of the hybrids. The wing bar of the Dark Brahma male dominates over the black wing of the Minorca, but it dominates imperfectly. 3. Comp.—In all cases the pea comb of the Brahma dominates over the single comb. Critical examination shows, however, that the pea comb of the hybrid is not always typical. Frequently the whole structure, and espe- cially the median ridge, is abnormally high (fig. 21), and, on the other hand, in a few cases the lateral ridges are hard to make out. The dominance is imperfect.** 4. KARLOBE CoLor.—The earlobe in every case contains both white and red. The result is not a blend, however, but is particulate, the white appearing at the center. As red is rarely wholly absent from the Minorca’s earlobes, whereas white is wholly absent from that of the Dark Brahma, it may be possible to bring inheritance of earlobe color under the general formuJa and speak of the white earlobe as being imperfectly dominant. 5. Irts Cotor.—Theiris of the hybrid is yellow, rarely with a trace of red or reddish brown. ‘The type of the Dark Brahma is dominant, but imper- fectly so. 6. BEAK AND Foot Cortor.—This is always black in the hybrid. However, the black is rarely the blue-black of the Minorca, but it is usually a brownish black frequently tinged with yellow, particularly on the under side of the toes. Black is imperfectly dominant. 7. Foot FEATHERING.—In allcases the hybrids have feathering on the feet. In many cases this is clearly reduced in amount from what is found in the Dark Brahma. Foot feathering is imperfectly dominant (fig. 20). 8. VuLtuRE Hock. —This is absent in every case, although about a quarter of the cases show the feathers of the heel much larger and more removed * The inheritance of the pea comb of the Dark Brahma has not been considered in the recent studies of others. The pea comb of the Indian Game is found by Bateson and Saunders (1902, p. 94) to be imperfectly dominant over the single comb of the White Leghorn. 36 INHERITANCE IN POULTRY. from the foot than in the Minorca. Plain feathered heel is dominant, but not perfectly so. CONCLUSIONS. This series of experiments is only begun. Conclusions as to dominance are tentative until tested in the second hybrid generation. The Minorca characteristics appear to dominate in (1) general black color, (4) white ear- lobes, (6) black foot and beak, and (8) absence of vulture hock. Dark Brahma characteristics appear to dominate in (2) wing bar, (3) pea comb, (5) yellow iris, and (7) foot feathering. In every case, however, dominance is imperfect. In some cases, at any rate, (5,7), it is the new, additional, or positive characteristic that dominates. Series VI.—White Leghorn and Dark Brahma. STATEMENT OF PROBLEM. THE RACES AS A WHOLE. It is proposed to investigate the behavior of characteristics when the heavy- bodied, short and stout legged, loose-feathered, dark-colored Asiatic type is crossed with the slender, tall-legged, close-feathered, white Mediterranean type. Both types are ancient, but the Brahma must be regarded as nearer its ancestral form, Aseel-Malay-Indian, than the Leghorn is to the Jungle fowl. TABLE OF CHARACTERISTICS. No. Characteristic. | White Leghorn. Dark Brahma, female. Bate cas 1 | Hacklecolor..... Wihiter ae crisis Straw, black-penciled...| Black, straw- laced. 24| Wing ibars sy cc Wihitese.-s.: .. | Buff, black-penciled ...| Black, red, and | white. 3 | Wing bow.......-. Wihttel--ecirace | Buff, black-penciled . Black and white. Ay elailicolors ci...) AMNES SA Ce 8 Soe Black, straw-penciled.. | Greenish black. Sa BCOMD tacreveloraeierere | Single (page 19) . Pea (see page 32). 6 | Earlobe......... White, red-edged Red (see page 33). ; (page 33). 7, | lrisicolor 4-4) eau (pages3)-re Yellow (see page 33). 8 | Vulture hock..... | PAtbsentsijecec cine | Present (see page 34). 9 | Foot feathering..| Absent ... Present (see page 34). to | General form.... | Narrow, slender. .| Broad, chunky. REMARKS ON THE CHARACTERISTICS. 1. HACKLE CoLor.—Among most poultry that are of broken color the hackle feathers are unlike those of the rest of the plumage. They havea dark center and a lighter lacing. Inthe Malays and Indians they have a red center edged with green. Inthe Gallus bankiva female the hackles have a black center (with straw-colored shafting) and straw-colored lacing. This is the type of hackle feather found in the male Dark Brahma. It is found, WHITE LEGHORN AND DARK BRAHMA. 37 in both sexes, among many other breeds. The hackle of the female Dark Brahma (fig. 18) differs from that of the male in that the broad black center is barred, or penciled, with straw color. 3. WiNnG Bow.—The wing éarv is described for the male at page 32. Inthe male Dark Brahma the feathers of the fourth and higher rows of wing coverts have their distal halves white forming the wing bow. Nosuch distinct wing bar and wing bow occur in the female, the feathers of this region being uniformly penciled like the others. MATERIAL. There are two sets of experiments in thisseries. Inthe /s/se¢the mothers were White Leghorn Bantams, Nos. 127 and 128, probably heterozygotes with black, further discussed at page 39. The paternal Dark Brahma, No. 122, has been already referred to at page 34. In the second set the mother was Dark Brahma, No. 12t. She has the same history as No. 122. She is a prettily penciled bird (fig. 18). The father was White Leghorn Bantam, No. 126, described at page 39. RESULTS. Of the first set 19 offspring are recorded, including 8 in the shell. Females 8, males 5. Of the second set 27 are recorded, including 8 in the shell. Females 14, males 4. I. GENERAL PLUMAGE Coror.—The result differs in the two sets and the two sexes, and it is otherwise variable. | Females. Males. Unknown sex. Plumage; color. | First | Second Total, | First Second| Total, | First | Second) 644) aera: | set. set. s set. set. 2 set. set. < | Nearly pure white ........ 4 3 7 3 2 5 7 II 18 30 White + much black | | and red pigment as | } Part TN pyeteer see eereeacecsres to) Cre ° 2 ° By \inotseca | 2 2 4 Like Dark Brahma fe- | | Be CN eer erconcencanenoecuroK| 4 | 3 *7 ° ° 9 7 Barned iiestsceecterssectens | Ol | 3 3 ° Ze, li, 72 5 Black or nearly $O..veveee+) OF ae 5 ° ° sO) 5 The results are explicable on the hypothesis that all of the White Leg- horn Bantams, Nos. 126 $, 127 9, and 128 2, contain white gametes and also gametes bearing red pigment, black pigment, and the barred pattern. 3. WING CoOLORATION.—In the /ivs¢ se¢ the wing coloration is like that of the plumage in general, except that in the females marked like the Dark Brahma the coverts contain much red (fig 23). Second set. Of 7 prevailingly white hybrids three show red or buff on the wings; +} of the 5 black-and-white (penciled) birds all but one show red or purple on the wings ; of two adult black hybrids one shows buff. Three other , * Fig. 23. { Fig. 25, Plate vit. 38 INHERITANCE IN POULTRY. females are marked like the Dark Brahma female. Red pigment is com- moner in this set, with White Leghorn father, than in the first set, with Dark Brahma father. ‘This speaks for the hypothesis that red has come from the White Leghorn, as, according to usual e xperience, the father tends to determine coloration. 4. Tat CoLtor.—/irst set. Of 11 offspring, 8 have a white tail, the prevail- ing color of the body; in one case the tail is white except for one black feather, and in two cases it, like the body in general, agrees with the Dark Brahma female in being black with buff penciling (fig. 23). Second set. Of 15 hybrids, 6 are nearly or wholly white on the tail, one has two black feathers, 5 are black, two are black-and-white barred, and one is black with buff, as in the Dark Brahma female. ‘The tail color tends to resemble that of the general body. 5. Comps Form.—In all cases of adult hybrids of either set, the comb is pea (fig. 24). Pea comb is consequently here also dominant over single comb. 6. EARLOBE.—Both the Brahma solid red and the White Leghorn white, red-margined earlobes appear in about equal numbers. It is probable that my heterozygous White Leghorn bantams have been early crossed with some red-lobed race. 7. Irts CoLor.—This is definitely established only in mature birds. All eyes show more red than the Dark Brahma and the tendency is to redden with age; consequently red is probably dominant. 8. VuLtruRE Hock.—This is absent in all cases (fig. 22). One hybrid has the hock feathers a little elongated. Short feathering at the heel is dominant. 9. Foor FEATHERING.—First set. Of 19 hybrids having the Dark Brahma father, 3 unhatched chicks are recorded as non-booted. Of the remainder, 8 are slightly or very slightly booted. Three adults have a medium covering of feathers on the foot. The Brahma tendency toward booting has been diluted by the cross with the Leghorn. Second set. Of 24 offspring of Dark Brahma mother, all have well-devel- oped boots. This constitutes a striking case of a difference in reciprocal crosses. Booting is probably here, as elsewhere, dominant, but frequently very imperfectly so. CONCLUSIONS. Of the nine characteristics, the following exhibit clear alternative inherit- ance, the dominant characteristic being printed in italics : Pea comb vs. single comb. No vulture hock vs. vulture hock. Booted foot vs. unbooted (when Brahma is mother). The other characteristics can not for one reason or another be so easily classified. The red of the wing bar seems to behave like a unit character and is independent of the coloration of the rest of the body. BLACK COCHIN AND WHITE LEGHORN. 39 The inheritance of booting is peculiar in that in the first set, Leghorn mother and Brahma father, the booting fails to show that clear dominance which is almost universal ; yet I can hardly suspect the purity of the Dark Brahma male. It would seem that in this series also the mother transmits booting more strongly than the father. Series VIIL—Black Cochin Bantam and White Leghorn Bantam. STATEMENT OF PROBLEM. This experiment was undertaken to learn the method of inheritance where one parent is pure white and the other pure black. THE RACES AS A WHOLE. The Black Cochin Bantam, also called Black Pekin, is a diminutive of the Cochin (fig. 26). It is stated by Wright (1902, p. 499) that the Pekins came in 1860 from the city of that name. ‘The original color was buff ; the black has probably been engrafted on the race by a cross with some small black race. The Cochins are closely allied to the Brahmas and share with them a chunky form, stout and densely feathered feet and red face and ear- lobes. The White Leghorn has been discussed at page 18. TABLE OF CHARACTERISTICS. | Daas Black Cochin | White Leghorn | No. | Characteristic. | Bantani | BAntagl ai lie eee Ba 1 | General plumage color.| Black. .... .. | White. |) §2) || (Harlobeycolor: 45... -/.- Red wae vucu seas | White, with trace of red. es Multune shocks nis ec =)-1: IRTESEN tor rerio | Absent. (hee | Foot feathering....... | Present........ | Absent. REMARKS ON THE CHARACTERISTICS. 1. GENERAL PLUMAGE CoLor.—In the Black Cochin this is a deep greenish black. No trace of white appears anywhere. 2. EARLOBE CoLtor.—In the Black Cochin this is of the dark red or bay characteristic of all the Aseel-Malay group. 3. VULTURE Hock.—This is well developed in the Black Cochin (see page 34). MATERIAL. The mothers were four Black Cochin Bantams,* very similar, each heavily booted and weighing about 600 grams apiece. Trap nests were not used, but owing to special peculiarities the eggs of the separate mothers were dis- tinguished as A, B, C, and D. The father was a White Leghorn Bantam, No. 126, purchased January, 1905, from the Cyphers Incubator Company, together with two hens (Nos. *Nos. 129, 130, 131, 132, received February, 1905, from Mr. H. B. Kutschbach (fig. 26, pl. rx). 40 INHERITANCE IN POULTRY. 127, 128). Mated with the hens, nine young were produced. Four of these were typical White Leghorns without black ; three others were white except that black feathers occasionally appeared. One (No. 213) was nearly solid black and one (No. 229) was black with nearly every feather barred with white. It is plain that the strain I have has not been wholly purified of black. This is indicated also by the fact that No. 128 has every feather peppered with black—a heterozygous form of coloration. RESULTS. 1. GENERAL PLUMAGE CoLor.—Of 26 hybrids, 11 were pure white or had only a little black ; 7 were black, sometimes with a little white, and 8 were barred black and white (fig. 27). The results confirm the view that White Leghorn Bantan No. 126¢ has black germ cells. The barred condition is unexpected and is probably recessive in the White Leghorns. 2. EARLOBE CorLor.—In all cases (10) ofadults but two, the earlobe is red ; in the remaining two some white is mixed with the red. The red earlobe is probably dominant, but imperfectly so. 3. VULTURE Hocx.—Out of 13 cases 11 have clearly no vulture hock and two show a slight enlargement of the heel feathers. Vulture hock is prob- ably recessive. 4. Foot FEATHERING.—Every hybrid is booted, but the booting is less heavy than in the Dark Brahma (fig. 27). Booting may be dominant, but it is not perfectly so. CONCLUSIONS. The male parent is heterozygous and probably contains at least three sorts of gametes, viz, pure black, pure white, and barred, the last being a mosaic.* The black of the mother is recessive to allofthese. The occurrence of barred mosaic is of interest, but itis of unknown origin. The ancestral red ear-color and the new ‘‘booting’’ are both dominant. Dominance is, however, im- perfect. Series VII].—White Leghorn Bantam and Buff Cochin Bantam. STATEMENT OF PROBLEM. This series was undertaken to determine the method of inheritance of buff when combined with a white plumage coloration. THE RACES AS A WHOLE. The White Leghorn Bantam has been described at page 39. The Buff Cochin Bantam (fig. 28) is a diminutive Buff Cochin, which resembles in form the Black Cochin (p. 39). Cochins as we know them to-day (the name was formerly applied to a different, now extinct, race) seem to have been imported into this country and also into. England from eastern China * Castle and Allen, 1903, p. 606. WHITE LEGHORN AND BUFF COCHIN. 41 in the year 1847. The earliest importations were buff. According to McGrew (1904, p. 526): In many of these retreats, #7-aws or monasteries, thousands of specimens of Buff and Partridge China (Cochin) fowls are annually raised, and in other places the colors are mixed. The Kinkee (gold flower) colored birds are the most esteemed, both as regards antiquity and purity. ... Hoangho is the oldest [of the] 77-aus, and its records show that this same race of fowls was cultivated by the brotherhood 1,500 years ago. Buff and Partridge Cochins are indigenous to the temperate and more southerly por- tions of the empire. This is corroborated by naturalists and travelers. Mr. Gabb, the well-known English naturalist, says: ‘‘According to my view, a black or white Cochin is an improbability, if not an impossibility, as a natural product of a tropical or subtropical region. The natural color of the feathers of the poultry in the zone of Cochin China would be buff or yellow, or some of the varieties of these colors, but never black or white, except by accidental variation.”’ Other testimony presented by the same author is of the same sort and establishes the fact that Buff Cochins are a primitive, foundation race of great antiquity. TABLE OF CHARACTERISTICS. Z | ex Discussed BuihCochin: Discussed | ae [fore | No. | Characteristic. | White Leghorn. | at page— | | at page— | = | | ——— | | | I | General color....... | MsreaAG =| 19 | EAS sSoace | 41 2 Earlobe color....... \WiAstleSeo0G5 sees 33 | Red.. 5 33 3 | Wulture hock........ INDSET tse eyveterefeveiere Wispetsortns | CERES EASES: | White Leghorn. | at page—| RumplessGame. | at page: iT | General color. ...| White............ | 18 | Black and red..... 25) Beaki colores. Wellowsiierereyacrst-teis 1g DENG Sagas oaoeods 3 | Uropygium.. .. .| Present ......... | ae Absentee. ci sees | a 4 | Foot color....... le WelLOw)y-sfe sletorensi= | 20 | WYABWE\ coon cboconac | 48 REMARKS ON TIE CHARACTERISTICS. Uropycium.—The absence of uropygium is acharacteristic that has long been known among fowl, but there scems to be little knowledge of its inor- phology. In ordinary fowl there are five ivee caudal vertebrze, followed by a fused portion—the uropygial bone. In the case of a rampless Game female (No. 1109, fig. 45) dissected by me, there are two unsymmetrically formed and intimately fused vertebrae behind the fifteenth synsacral—the posterior limit of the sacral vertebree. That there are two is shown by distinct trans- verse processes with spaces of the passage of the nerves. Behind these is a knob of bone about r mm. in diameter. These three elements constitute the entire caudal skeleton. It is profoundly reduced from the normal. Rumplessness may be found in any race. It has cropped out in two of the 800 fowl bred at this station in the past year—hybrids derived from the Minorca-Polish aud the Leghorn-Houdan crosses. It seems like a misuse of the term é7ced to speak of a ‘‘ Rumpless breed,’’ as poultry books do. The characteristic is referred to by Aldrovandus in 1645, by Temminck, and by other early writers. Its origin has been ascribed to Persia, to Cey- lon, and to China ; doubtless it occurs in all these places as well as in many others. ‘Taillessness early appeared among fowls in America. Clayton (1693, p. 992) asserted that he had observed that in ‘‘ Virginia’’ most of the cocks and hens were without tails, and Wright states that he was informed by a West Indian in 1872 ‘‘that the greater number of fowls in his own neighborhood had no tails.’’ Darwin (1876, Chapter VII) refers to this characteristic and states that one bird he examined had no oil gland; the same is true of the three rumpless Games that I have had. Among the 62 INHERITANCE IN POULTRY. poultry books that describe the ‘‘ breed’ quite fully are Tegetmeier (1867, pp. 230-232), Baldamus (1896, pp. 170-172, ‘‘ Kaul oder Klutthtihner’’ ), Durigen (1886, pp. 98-100), Wright (1902, p. 481), and Weir-Johnson- Brown (1995, pp. 1016-1017). Regarding the inheritance of this characteristic, statements are not in accord. Tegetmeier (p. 231) says: A friend of mine purchased asuccessful pen [of Rumpless fowl] at a poultry show, taking them away to a walk where no other fowls ever trespassed, and yet the chickens were, in a considerable number of instances, furnished with fully developed tail feathers, being not rumpless. On inquiry of the previous owner, he stated: ‘‘Mine have always done so from the first time I kept them; but the tailed birds will very probably produce rumpless chickens.’’ Three such birds were purposely retained, and they produced the next year more than twenty youngsters, all of which but one were rumpless and destitute of tail feathers. The foregoing experiment would seem to prove that the rumpless parents were heterogametous, and that while rumplessness is dominant the recessive condition of tail is here prepotent (Castle, 1905). Darwin (1876, Chapter VII) possessed a rumpless bird which ‘‘came from a family where, as I was told, the breed had kept true for twenty years; but’’ he adds, ‘‘ rumpless fowls often produce chickens with tails.’’ ‘The breeding true of a character may mean either that it is dominant and homogametous in this respect or that it is recessive. Durigen (1886, p. 99) states that a rumpless cock mated with a tailed hen produces not exclusively rumpless, but a fair percentage of them, and Wright (1902, p. 481) says that ‘‘a Rumpless fowl crossed with any other generally produces a large majority of Rumpless birds.’’ All of the fore- going results are consonant with the conclusion that rumplessness is typically dominant, but that the recessive full tail may be prepotent. MATERIAL, The mother was the White Leghorn bantam No. 127 discussed at page 39. She is heterozygous and contains black gametes. The father (No. 117, fig. 46) was one of three rumpless bantams obtained from Dr. A. H. Phelps, of Glen Falls, New York. ‘Two of these were typical Black-breasted Red Games; they lack oil glands and weigh about 1,000 grams each. RESULTS. Only the first generation of hybrids has been so far obtained. GENERAL PLUMAGE CoLor.—Of 24 hybrids 12 were white or prevailingly so (fig. 47). Usually, however, more or less black and more rarely some buff was present. The other 12 were either black-and-white barred (and these were all males) or black with more or less reddish. As we have seen, the white mother contains recessive black or black-and-white, so that the result accords with the expectation of only 50 per cent white. BLACK COCHIN AND RUMPLESS GAME. 63 BEAK Co_or.—In the hybrids the beak is sometimes yellow, sometimes black, sometimes black-and-yellow streaked. Urorycium.—Of 24 hybrids the uropygium is normal in 23 (fig. 47). One chick taken from the egg is recorded as without tail, though tail gland is present. It is doubtful if much stress may be laid on this record, as the uropygiuim is always very small in the unhatched bird. We may exclude it from present consideration. [This whole result was unexpected because opposed to the earlier observations. It leads to the provisional hypothesis that rumplessness is recessive in my strain. If full tail is recessive, then in my strain the recessive condition is prepotent. Further discussion must be deferred until the second hybrids have been bred. Foor CoLtor.—This was yellow in about half of the cases and willow or dark in the other half. Recalling that the White Leghorn is heterozygous, the result favors the hypothesis that yellow is dominant over willow. CONCLUSIONS. White plumage color seems to be dominant over game color. ‘The hy- potheses seem to be warranted that yellow beak and foot color are dominant, and that rumplessness is recessive in this strain. Series XII],—Black Cochin Bantam and Black Breasted Red Rumpless Game, STATEMENT OF PROBLEM. This cross was primarily to test the inheritance of rumplessness, and secondarily of black against red plumage color. THE RACES AS A WHOLE. Concerning the Rumpless Game see page 61. ‘The Black Cochins are discussed at page 39. TABLE OF CHARACTERISTICS, No | Characteristic Black Cochin | Discussed | Black-breasted Red | Discussed 2 3 Bantam. | at page— | Rumpless Game. at page— “ale —— - — — |- = | —— —o r | General (color. .).|| Blacks.7...-\1/-- | 39 Red with some black. 62 2 | Uropygium...... leet esen creeper 63 PAlbsentrncteitesicerr ee | 63 3yn |Piristcoloneetencer | Dark brown ..| a | Red streaked wit | | I pyellowrce-- Bretcrs)| 4 | Vulture hock ...| Present...... 39 INDE MeoD GooGboe oso 5 | Foot feathering..| Present....... 34 lPAlbserithasrinesticrice | | | MATERIAL. Mothers.—The Black Cochin Bantams Nos. 129 (fig. 26), 130, 131, and 132 were the same as those referred to at page 39. Father.—The Rumpless Game is No. 117, referred to at page 62 (fig. 46). 64 INHERITANCE IN POULTRY. RESULTS. Only the first hybrid generation has been produced. GENERAL PLUMAGE CoLor.—Of 24 hybrids all were prevailingly black. Among 18 of those that hatched 8 showed some red. ‘This red is chiefly found asa lacing on the hackle feathers or a peppering on the wing coverts,* throat,} and outer margins of the remiges.{ This seems to point to the hypotheses that while black dominates over red the dominance is sometimes imperfect. When red occurs it occurs on those feathers that normally con- tain red in the Game, and on that part of the feather that is red in the Game. UropyGium.—This is invariably present, apparently fully developed. Ir1s Coror.—All the hybrids have dark-brown eyes; only one shows a trace of red. The hypothesis seems justified that in this case dark-brown iris pigment is dominant over red and yellow. VULTURE Hocx.—This is always absent. In only a single case§ are the feathers slightly elongated on the hock. Foot FEATHERING.—KEvery chick that hatched has the foot and at least one toe booted. In some cases this booting is much reduced as compared with the Cochin parent. Booting is dominant, but not always completely so. CONCLUSIONS. In this cross of black vs. red, black appears to be dominant, although im- perfectly so. The two colors do not blend, however, but red appears in a particulate fashion, usually in the parts of the plumage that have normally least black pigment. It is as if there were a struggle between the two pigments and red overcame black where black was weakest. The presence of tail in the first hybrid generation is confirmatory of the results of the preceding series. Rumplessness is apparently recessive. Brown iris color appears to dominate over the older red, and booting dominates over the ancestral clean-footed condition. * Nos. 589 ¢' and 798 ¢. Tt No. 587 2. t No. 577 2. § No. 651 o. GENERAL DISCUSSION. 65 D. GENERAL DISCUSSION. INHERITANCE OF PARTICULAR CHARACTERISTICS. COMB FORM. The comb is a characteristic that has had its origin in the genus Gallus. It consists of a mass of uncovered erectile tissue—a tissue present in many species of birds. The primitive form of the comb is the single comb seen in the wild species of the genus Gad/us, and in most domestic races. This may be modified in two directions : First, in the direction of lateral repetition of the comb giving rise to the pea comb,* and, in an extreme case, to the rose comb (of which the walnut comb of the Malays is a special modifica- tion); second, in the direction of reduction of the modified comb producing the races with mere papillee (Houdan, Polish, La Fléche, etc.) or that are entirely combless (Breda fowl). That the rose comb is a modification of the same sort as the pea comb but carried to a greater extreme is indicated by the fact that the rose comb often shows five parallel ridges (instead of the more usual irregularly scattered papillz) and that in the female the rose comb sometimes consists of three ridges as in the male pea comb. When single comb (Minorca, fig. 4) and pea comb (Brahma, fig. 19) are crossed, pea comb is dominant (p. 35). The median ridge is, however, in the hybrid high for a pea comb and the lateral ridges are usually reduced (figs. 20, 21). When single comb (Leghorn) and rose comb (Minorca) are crossed, rose comb is dominant (p. 30). When single comb (Minorca or Leghorn) is crossed with the paired rudiments of a comb found in the Polish and Houdan fowl, a Y-shaped comb results (pages 10, 22, 28, fig. 8). This Y comb is of great interest. It was obtained by Bateson and Punnett (1905, pp. 108, 112-114) in some of the offspring of (single-comb Leghorn x rose- comb Dorking), crossed with (single-comb Leghorn x walnut-comb Indian) ; and also in one of the offspring of a single-comb Leghorn crossed with [(single-comb Leghorn x walnut-comb Indian) x (single-comb Leghorn x rose-comb Dorking)]. In Bateson and Punnett’s cases the splitting was evidently nearly complete, forming an O-shaped comb, or the ‘‘ cup comb”’ of Darwin (1876, Chapter VII). The Y comb was obtained also by Hurst (1905, pp. 133, 135, 138, 140, 146). This was a single split comb when Leghorn and Houdan were crossed, and a rose split comb when rose-comb Hamburgh and Houdan were mated. The interrelation of the different forms of comb—single, pea, walnut, y, and V may, I think, be expressed in the following hypothesis: The pea comb and the walnut comb are composed of two elements—a median single comb and a pair of lateral combs. This hypothesis is supported by the * The pea comb was doubtless a characteristic of the unknown feral ancestor of the Aseel-Indian group. But as the single comb is the dominant type in the known wild Jungle fowls the pea comb probably evolved from it. 5 66 INHERITANCE IN POULTRY. following evidence. First, of teratology. Extraneous paired papillee occa- sionally occur on the sides of the single comb in pure-bred races. These are known as ‘‘ side springs,’’ and are considered by fanciers as grave ‘‘ defects.’’ Now such side springs are morphologically equivalent to the lateral ridges of the pea comb. Second, there is the evidence of hybrid forms. Bateson and Punnett (1905 2) show that when pea comb and rose comb are crossed the second hybrid generation (F,) gives single comb, as well as pea and rose combs. This result may be interpreted as due to the fact that the gametes of a pea- combed bird have either a tendency toward side-springs (= pea comb) or they have no such tendency (= single comb); and the gametes of a rose- comb bird have a tendency to produce two pairs of side combs (= rose comb) or else they have no such tendency (—single comb). When two gametes without the side-comb tendency come together in F, a single comb is pro- duced. The necessity of assuming absence and presence of lateral combs strengthens the view that the pea comb is made up of two elements—median and lateral. If median comb and side-springs are distinct elements, then they should be independently inheritable. This result is realized on the one hand in the single comb, and, I think, on the other hand, in the cup comb (fig. 6), which consists of two side-springs without median comb. It is realized also in the V comb of the Polish fowl, which is a cup comb of which the anterior portion is typically not developed. That the V comb represents the posterior portion of a cup comb is supported by the fact that it is not uncommon to find not one pair of papille merely, but two, three, or four pairs of papillae in Polish fowl and in second-genera- tion hybrids. A row of three or four papillae on each side of the head is a close approach to a typical cup comb. The incompleteness of the cup comb where a VY comb is produced may be due to various causes. In the Polish fowl the upturned nasal process and absence of a bony ridge over the nostrils appear to be the cause of the absence of a comb there, and we have seen (p. 17) that the only undissociable char- acteristics in the second-generation hybrids of Minorca and Polish are those of high nostril and rudimentary comb. ‘The second cause restricting the development of the cup comb to its posterior limits is the presence of a median comb anteriorly ; thisis the case of theordinary Ycomb. The Ycomb is found in hybrids between single and VY comb; the anterior portion of the comb is not suppressed here, because the bony roof of the culmen is com- pletely developed, and the very presence of a large median comb there prevents the development of theside-springs at the same niveau. In the development of the comb of the hybrid there is, as it were, a struggle between the two elements of median and lateral combs. The Ycomb assumes a great variety of forms, rupning the entire gamut from a single comb on the one hand to (1) a cup comb or to (2) a pair of papillae on the other. I have already (p. 10) referred to the variation of the length of the stem of the Y, series INHERITANCE OF PARTICULAR CHARACTERISTICS. 67 (1), from 100 per cent tonearly zero. The second hybrids of Polish or Houdans crossed with single combs illustrate series (2). We begin witha single comb having its posterior one-sixth split ; next comes a comb having its posterior one-sixth split and anterior five-sixths single, but greatly reduced in height (fig. 50); next the same with the anterior portion reduced to an irregular carunculated mass having a slight median elevation (fig. 49), and finally a pair of papille only (fig. 48). In this series we have a fading out of the median portion, part passe with the enlargement of the nostril, but the persistence of the side combs unimpaired. ‘The side combs have been unable to enter the territory from which the median comb has been driven, because that territory is likewise untenable for it. These two series sufficiently demonstrate that the Y comb represents the posterior portion of the cup comb. That the cup comb represents merely the greatly enlarged lateral combs or side-springs is proven by the occasional presence of both median and cup comb on the same individual. In some races, as in the English type of Hou- dans, the median comb typically appears lying between the pair of cup-like side-springs, resembling the trunk of a butterfly between its wings. Among the heterozygous combs of the second generation of Minorca x Houdan or Minorea x Polish hybrids, instructive examples of persistence of both single comb and side-springs are especially apt to occur. Figure 52 shows this condition ; there is a median comb anteriorly and a nearly typical pea comb posteriorly, except that the lateral ridges are atypically high. Thus the Y comb becomes explained as due to the presence of both single and lateral combs. The question now arises, Is it possible to explain on Mendelian principles the production of a Y comb when median comb and lateral comb are crossed ? In accordance with such principles we should have to picture the gametes of the single-comb and \y-comb parents as follows: Single comb. | V-comb, | | | No median elements. | Lateral elements. | Median element....... No lateral elements .. The allelomorphs are then median and no median, no lateral and lateral, and the positive characteristics are dominant. In the second hybrid gen- eration the two dominant characters should be combined in nine-sixteenths of all cases; the two recessive in one-sixteenth, and one dominant with one recessive in three-sixteenths ++ three-sixteenths of the cases. Another hypothesis is possible. Granting that the Y comb is no neomorph, but the sum of single and lateral comb, then the Y comb may be a case of particulate inheritance, the median comb being produced on the anterior and the lateral on the posterior part of the frontal region. In cases of particulate 63 INHERITANCE IN POULTRY. hybrids bred znfer se, the offspring exhibits one or the other of the parental conditions each in 25 per cent of the cases and the heterozygous condition in 50 per cent. ‘Todecide between these rival hypotheses we have to appeal to the statistics of occurrence of the different forms of comb. All cases (Series I and II) are combined in the following table, showing distribution in the second hybrid generation : Expected. Comb characteristic. | i Actual. | On hypothesis ae aoe | of dominance. | ° (SPARSE | inheritance. ~ Per cent. Per cent. Per cent. Singleicontby.-a- teeter 18.75 25 30.1 VW CHM) oan paccaoosesce 56.00 52 44.9 Wateralicombsys easel) ekOu75 5 25 25.00 IN OCosl i sp sooogusehouaSr | 16:25 370 ° o? The foregoing table reveals several things. First, the actual distribution of comb form in the second generation accords better with the hypothesis of particulate inheritance than that of dominance of both single and lateral comb. That there is an excess of single comb and deficiency of Y comb is partly accounted for by occasionally counting a potentially Y comb but actually single (or nearly single) comb as a true single. Secondly, the hypothesis of dominance demands the occurrence of a fourth form—pre- sumably no comb—in 6% per cent of the cases. No combless fowl was raised to maturity, and the only possible cases were seen in still very young or unhatched chicks. Probably no true combless bird appeared. From both of these considerations I conclude, provisionally, in favor of the theory that the Y comb is reproduced from the median and the lateral by particulate inheritance. NOSTRIL FORM. The sum of results in Series I, II, and III (narrow x high nostril) gives : Narrow and intermediate. | High. Generation. l Jj. | Actual. | Expected. Ye | Actual. Expected. | Per cent. | Per cent. | Per cent. | Per cent. Eanharesaysrcien Metetsroueysists | 102 |} 99.0 | 100 Tit 4} 1.0 | ° aren fetsicieleiiietsies | 99 | 73-9 | 75 35 | 26.1 | 25 Hy Darrow...) || 33 | 51.5 | 50 300 48.5 50 A close agreement exists between the percentage obtained in each genera- tion and the expectation on the Mendelian theory, assuming that narrow nostril is dominant. The statistics do not, however, tell the whole story. In 36 per cent of the cases in the F, generation the nostril was wider than in INHERITANCE OF PARTICULAR CHARACTERISTICS. 69 the ‘‘narrow’’ ancestor. Even inthe F, generation nearly half of the ‘‘ nar- row and intermediate’’ were of the intermediate sort. This intermediate form is evidence that dominance is imperfect and segregation is incomplete. CEREBRAI, HERNIA. Cerebral hernia is, as already pointed out, a typical monstrosity. The distribution of its occurrence in crossing is as follows : lade Re | F, x plain. Crosses. Plain. | Hernia.) Plain. | Hernia,| Plain. | Hernia. Minorca >< Polishes .vccciej.% | 66 ° 75 23 34 fo) White Leghorn X Houdan. .| 24 ° 34 II 25 fo Houdan X Minorca Se | 16 ~21(0) ae a te ae ARO tales: <;crtersrroer eis | 106 fo) Tog | 34 CO 59 fo) | = — ————] — Rercenta gels |ccey-icles)sieteies | 00 ° 70.1 23.9 100 ° *Excluding one case of egg embryo with cerebral vesicle. 7 Excluding one egg embryo recorded as doubtful. Cerebral hernia is inherited in Mendelian fashion with plain head domi- nant. Nevertheless, many of the plain-headed hybrids have the frontal eminence abnormally high—dominance is imperfect. CREST. The crest is independent of the cerebral hernia (pages 16-18). It isa widespread characteristic among birds, so common that it is not readily thought of as pathological but usually as ornamental. The distribution of ifs occurrence in crossing is as follows: F,. 1 F, X plain. Crosses. = nn ee Plain. | Crested.| Plain. | Crested.| Plain. | Crested. Minorea < Polish -........ fo) 7o II 41 6 6 White Leghorn X Houdan.. fo) 25 6 13 6 9 Houdan X Minorca..... : fo) 9 d6 : by a Rrizzlepeoilky-eeeeee eee fo) (eo) 109 17 54 12 15 Percentage te. ski ° 100 24 76 44.5 55-5 Crest is inherited in Mendelian proportions, and is dominant over crestless head. Even when the Silky is crossed with Gallus bankiva its crest is domi- nant (fig. 53). In this case the new characteristic, a positive variant, domi- nates over the ancient one; but the crest is diminished in the first genera- tion ; dominance is imperfect. 70 INHERITANCE IN POULTRY. WHISKERS OR MUFF. This is certainly a new character and a positive variant. The distribution of its occurrence in crossing is as follows : | 125 | igh F, X plain. Crosses. | |) ees ‘Present. es Absent. | Present. | Absent. | Present. Leghorn X Houdan....... ? 26 5 II Houdan X Minorca......... oe | EE ee eee ——— IKaWNlemorocueodaaabad ° | 35 | ? | 26 «| 5 | II Muffling is apparently dominant. BEARD. This is also a new, positive, variant. The distribution of its occurrence is as follows | F,. | Hee F, X plain. Crosses. | | = | Absent. Present. | Absent. | Present. | Absent. | sear | ie = | — “se Leghorn X Houdan........ oO iN 4 ? | 12 3 8 Houdan X Minorca ° ce | 9 | | 35 | oe tan ee as eal a ———— Totalequsssectaoacneeen ly 330 Wil a | } 8 | Beard is apparently dominant, but often imperfectly so. FEATHER FORM. Silkiness is a new characteristic and, approximating as it does the juvenile down condition, anegative one. Whena Silky is crossed with a Jungle fowl the offspring are plain. Silkiness is recessive to non-silkiness—the retrograde to the progressive type. Frizzling is likewise a new characteristic—a positive character added to the perfect feather. The distribution of the occurrence of silkiness and friz- zling is as follows : Non-frizzling. | Frizzling. l | Re | No silkiness. | Silkiness. | Frizzle X Silky..... Ls 10 o | 4 6 | The Frizzle fowl used were doubtless heterozygous. When non-frizzled birds are crossed iz/er se they produce only plain offspring. Frizzling is dominant over non-frizzling—the progressive over the primitive. INHERITANCE OF PARTICULAR CHARACTERISTICS. eu UROPYGIUM. Rumplessness is a new characteristic and a typical negative variant. The distribution of its occurrence is as follows : F}. Non-rumpless. Rumpless. Leghorn X Rumpless Game....... 23 *o Cochin X Rumpless Game......... 19 fo) Frizzle X Rumpless Game.... .... 7 ° Nankin X Rumpless Game........ 3 fo) ARNE Baaonecoge coCOGNSS 52 fo) Percentage rice) leleisleisielersisl= boa 100 fo} * One egg embryo doubtfully rumpless. The new, zegative characteristic is here completely recessive. TAIL-LENGTH. The long tail of the male Tosa fowl is a new, positive variant. The dis- tribution of its occurrence in male hybrids is as follows : Hie F,. Crosses. | Short. | Long. | Short. | Long. ROSA aaa OCH Annee pyieretersie isis ieretel cloleters fo) 3 ? ? IhiabacKs< WWOLAwopavcouconbouKenoad ° *16 ANEM. SSC obdecconuecooguUsO OSS fo) | 19 * The tails are, perhaps, more properly intermediate. While still growing at date of record, they grow slowly. The new, positive characteristic is doubtfully dominant, possibly inter- mediate (cf. fig. 34). VULTURE HOCK. This bundle of strong feathers constitutes a new, positive characteristic. The GrSURI See of its occurrence is as follows : ie Bee Crosses. Absent.| Present. | Absent. | Present. Minorca X Brahma........-..-. "| La(0) Leghorn X Brahma............. 12 ° Black Cochin x een orn oe 12 (Small) 1 Leghorn X Buff Cochin.... .. 9 ° Ro Be Tosa X White Cochin. . ce 13 T3 16 $20 Bralimiay ee hOsa eerie) secs All grades. aA ore Black Cochin X Rumpless Game. Q 11 fo) * One shows trace of enlargement of feathers. tSeven recorded as slight. + Females with vulture hock ; males without it. § One case of trace of elongation of feathers. 72 INHERITANCE IN POULTRY. The result is peculiar. Usually the vulture hock is absent in the first hybrids, indicating its recessiveness. In crosses with a particular race— Tosa fowl—however, there is no recessiveness. It is probable that the Tosa fowl is heterozygous in respect of this characteristic. The new character- istic is recessive, but imperfectly so. FOOT FEATHERING. Foot feathering, as the discussion on page 34 indicated, is a positive vari- ation, new to Ga//us, but not of a pathological sort. Common among wild, scratching birds, its occurrence in Gallus may be regarded as a case of de- gressive variation (de Vries). The distribution of its occurrence is as follows : 186 nN Crosses. oO Non- Non- acted! Booted. bosted: Booted. Minorea X Dark Brahma...... I 4o Leghorn female X Dark Brahma Malee-r ease BAS 4 15 Dark Branma female x Leg- hornemales yn. ei eee fe) 25 Black Cochin x Leghorn...... (a) 20 Leghorn X Buff Cochin........ 3 26 oe ae Tosa X White Cochin ..... .. ° 7 7 48 Dark Brahma 5@ Losaie).j)e oh fo) 22 Sc Oe Eirizz lene oil kayjen eeiesieretelcnsierets 3 15 Black Cochin X Rumpless Game. te) 21 Photal Women yomrctperetcletclesteraters II IgI 7 48 The foregoing statistics tell only a part of the story. Booting, when present, is frequently much reduced ; one may regard absence of booting as the extreme condition. Booting is dominant, but usually imperfectly so. EXTRA TOES. The extra toe is a positive variation of a teratological sort. The distribu- tion of its occurrence is as follows : F\. Jey, } F, X normal. Ceoeeee Noextra| Extra | Noextra| Extra | Noextra| Extra toe. toe. toe. toe. toe. toe. Houdan X Leghorn....... 6 31 17 6 17 8 Houdan X Minorca....... 6 15 AF as bf ne Brizzlem<:Gilkeypecr ctleciele 7 23 Motallvesaereiictoest 19 69 17 6 17 8 Percentage ...... Rytabrleteres Ae | 73.4. 73-9 26.1 68.0 32.0 INHERITANCE OF PARTICULAR CHARACTERISTICS. Ue) These results are peculiar. If both normal-toed and extra-toed ancestors were heterozygous in respect to toes, we should expect the result obtained in F,. It is quite possible, though not probable, that thisistrue. Thenextra toe would be dominant, although sometimes so imperfectly so as not to appear. In F, the parents were normal-toed, either because ‘‘normal’’ is recessive or because it is imperfectly dominant. All offspring should be normal-toed in the one case or give 100 per cent to 75 per cent extra-toed in the other. The result is not in accordance with either hypothesis. If there is any dominance in this generation it is of the zorma/ toe. Bateson and Saunders (1902, p. 124), while concluding that extra toe is dominant, find ‘‘ that the recessive foot character may sometimes dominate.’’ Hurst (1905, p. 150) also got, in a cross between Leghorn and Houdan, some normal-toed offspring which, interbred, produced extra-toed progeny. He concludes that a usually dominant character may recede in certain individ- uals. There is danger here of straining Mendel’s law. It is better to hold ‘‘explanations’’ in abeyance until the matter of inheritance of polydactylism has been more thoroughly investigated. Certainly the facts of inheritance of polydactylism in man can hardly be explained on Mendelian principles (Davenport, 1904). Polydactylism is at least not recessive. The new, posi- tive, pathological characteristic holds its own against the older one. SKIN COLOR. The epidermis of poultry is everywhere covered by feathers except on the beak, face, and feet. The naked portions may, however, have a different color from the covered ones ; consequently the correlation between general skin, beak, and foot color, although not absent, is not close. Thus, although the yellow beak and foot of the Leghorn are correlated with its yellow skin, the black legs and beak of the Black Minorca are not accompanied by a black skin. Not all exposed parts, even of the skin, are of one color, for the face, at least, may be red or white when the legs are black. Color of beak and foot are, on the other hand, closely correlated, individual variations of the one being usually associated with corresponding variations of the other. This correlation is doubtless the result of the similar cornification of the skin of beak and foot, whereas (excepting races with opaque white face) the vascular face and earlobes are white or red, according to a less or greater blood supply in them. The pigmentation of the epidermis of poultry falls into three classes: (a) Without pigment or white; (4) yellow; (c) black. White skin is the com- monest, even among poultry with black plumage and feet. Yellow skin is found in the Asiatics, derived from the Aseel-Malay ancestry, and is a char- acteristic of the White Leghorn. Black pigment occurs in the skin of the Silky fowl and the Negro fowl. Black pigment is to be regarded as a new variant and of the nature of a pathological sport—melanism. When black 74 INHERITANCE IN POULTRY. skin is crossed with white, black—the new, positive, pathological character- istic—is dominant (page 60). MANDIBLE COLOR. The prevailing types are black, willow, yellow, and white. Black is the primitive color on the Jungle side; yellow, onthe Aseel group. When horn (Houdan) and yellow (Leghorn) mandible colors are crossed, the first genera- tion shows the yellow of the Leghorn, whichis dominant. When, however, the black beak of the Minorea was crossed with the yellow beak of the Brahma, the dark color dominated. The potency in the hybrid of beak color seems to follow this series: Black, yellow, horn. The most positive char- acter, black, dominates all. FOOT COLOR. Four principal types are to be distinguished—willow, black, yellow, and white. Willow is primitive and white the most aberrant. The results are based on still insufficient data, but so far as they go they indicate that willow is dominated by yellow (p. 54), yellow by white (p. 24), and white by black (p. 28). The newer, negative characteristic, white, is dominant over the older yellow, but the new, positive characteristic of melanism dominates all. IRIS COLOR. Of the various forms, pearl to yellow is characteristic of the Aseel type ; red, of the Game or Gallus bankiva type. Black has become associated with black plumage. The results, subject to revision, indicate that in poultry, as in man, iris color rarely blends, that red dominates pearl (page 38), and that dark brown dominates red. ‘The new, positive variation of melanism seems to dominate all, although not always perfectly. EARI,OBE COLOR. Red is primitive in both groups. White is a new variation, which is prob- ably due to fat or other particles in the skin, and is consequently positive. Only in extreme cases is red wholly eliminated from the earlobe. In three series of crosses (V, VI, and X) of the red-lobed Dark Brahma and a white (and red) lobed race the earlobes were prevailingly red, but had some white at their centers. Likewise, in two series of crosses (VII and VIII) of the red-lobed Cochin and a white-lobed Leghorn, red dominated in the hybrids, but did not always perfectly exclude white. Red is apparently dominant, but very imperfectly so; some cases rather indicate particulate inheritance. GENERATI, PLUMAGE COLOR. The original plumage as exhibited in the Jungle fowl is largely black and red; that of the Aseel type sometimes contains much white; but the pure white plumage must be regarded as a new negative variant. The outcome of crossing is complex. INHERITANCE OF PARTICULAR CHARACTERISTICS. 75 WHITE vs. DARK—Three different results may be, under differing condi- tions, obtained. Dominance of White.—This is the usual result. Two White Leghorns crossed by a black Minorca produced only white hybrids, but the female hybrids, at least, had some black feathers. White Leghorns crossed with Houdans gave only white. White Leghorns crossed with a Red-backed Game had white offspring with some buff on breast. On the other hand, the white color of the Silky dominates over the dark color of the Frizzle (Series XI) in about only 23 percent of the hybrids. Bateson and Saunders (1902, pp. 108-109), dividing all hybrids between black and white parents into those of light type and those of dark type, conclude that the former are to the later as 3.1 tor. Bateson and Punnett (1905, p. 117) conclude that offspring of a pure white parent with colored or heterozygous (mixed) birds are practically always prevailingly white. Hurst (1905, pp. 146-149) gets chiefly white birds from crosses of White Leghorn hens with black or mottled males. The exceptions may be due to the impurity of one of the females. Barring.—No barring resulted from crossing White Leghorn with Houdan or black Minorca, or Silky with Frizzle. On the other hand, all males, and only males, were barred in the hybrids of Tosa x White Cochin, and in the hybrids of White Leghorn Bantam and Rumpless Game barring occurred, but among males only. Of 26 hybrids between Black Cochin and White Leghorn, 8 were barred black and white, and these belonged equally to the two sexes. Of 11 dark hybrids obtained by Hurst (1905, p. 133) from White Leghorn x Houdan, 6 developed into black females and 5 into cuckoo males. Apparently barring (‘‘ cuckoo marking’’ of the English) is asso- ciated with maleness. This result is curious enough, for, as Darwin pointed out, in the ancestors of domestic poultry barring (or rather penciling) is confined to the female sex. Barring is a heterozygous condition found in hybrids from a white and a black parent. It is provisionally regarded as a form of particulate inherit- ance as opposed to the alternative inheritance of the Leghorn x Minorca cross. This heterozygous condition when interbred usually breaks up into white, uniformly pigmented, and barred again, as in the case of the Tosa x White Cochin hybrids (p. 49). This form has in certain cases, as in the Cuckoo Dorkings and in the Dominiques—ancestors to the Plymouth Rocks— become truly mosaic, transmitting the mixture of qualities pure. The method of fixing a heterozygous poy is still unknown to science.* “* The experience of beeen of mice ane guinea-pigs shows that one may be dee to the absence of an oxidizing ferment necessary to the bringing out of the color potential ina chromogenic substance (¢/. von Fiirth, 1903). If the chromogen is present the addition (by crossing with a pigmented individual) of the ferment will reveal in the hybrid off- spring the colors and pattern latent in the white parent. Working on this hypothesis, we can judge of the latent patterns in the White Leghorn bantams and draw conclusions 76 INHERITANCE IN POULTRY. Andalusian Coloration.—Among the offspring of a White Leghorn and a Black Minorca two adult blue fowls were reared (fig. 54). The coloration was that of the Andalusian ‘‘breed.’’ It consisted of a minute patchwork of black and white pigment. Such a bluecoloration is common in barn-yard fowls. It results, according to the testimony of breeders,+ from crossing black and white. The special conditions which determine whether the offspring of a white and a black parent shall be all white or barred or blue have not yet been determined. The solution of this problem offers one of the most interesting fields for future investigation (p. 30). WHITE vs. Burr.—Both colors are novel ; the former is probably a nega- tive mutation ; the latter has been extracted from the original game colora- tion of fowls. The hybrids are prevailingly white, and white may be regarded as dominant. Nevertheless, this dominance is imperfect, for in half of the offspring buff is more or less evident. It is found diffused over the back, wings, and breast as in ‘‘pile’’ Games. On the whole, white is less strongly dominant over buff than it is over black (Hurst, 1905, p. 134). BLACK vs. RED.—The red coloration is ancestral ; the solid black is novel and positive—a melanic condition. The hybrids between Black Cochin and Red-breasted Game are prevailingly black, but about half of them show red lacing on the hackle feathers or a red peppering in those places where red is displayed by the Game. Black is dominant over red, but imperfectly so. COLOR OF TOP OF HEAD. In the white-crested Black Polish the feathers of the top of the head are in striking contrast to those over the rest of the body. That the crest is not necessarily white is proven by the existence of a black-crested race. Hybrids between the Minorca, whose head is wholly black, and the Polish give (p. 15) chiefly black feathers in the males, the females, however, still showing as to what pigmented ancestors they may have had. They were used in five crosses, as follows : (1) Black Cochin X White Leghorn ; (2) White Leghorn < Buff Cochin ; (3) White Leghorn x Black-breasted Red-backed Game; (4) White Leghorn X Dark Brahma ; (5) Dark Brahma X White Leghorn. Taking all offspring together, about 50 per cent (48.5) are white or nearly so. All crosses exhibit barring, together in about one-quarter (26.5) of the cases, and also black and buff or red. It seems probable that all of these pigments and the barred pattern are latent in my White Leghorn bantams. These conclusions are supported by breed- ing the White Leghorns zzfer se, when, in addition to white offspring, a black and a barred were obtained (p. 4o). Similarly among the second hybrids between the Tosa and White Cochin Bantam there appeared’a male and a female resembling in plumage colora- tion the Partridge Cochins (p. 49). This coloration probably lay latent in the gametes of the White Cochin. + Compare Darwin (1876, I, Chapter VII ; 1894, I, p. 270); Wright (1902, pp. 291, 292, 317, 301, 399, 401, etc.) ; Bateson and Saunders (1902, p. 131); Bateson and Punnett (1905, p. 126). When blues are interbred, the offspring are either white or black or blue. Even in the Andalusian “‘ breed ’’ the blue coloration has never become fixed. INHERITANCE OF PARTICULAR CHARACTERISTICS. “fat white in their crests. The hybrids crossed back on the Minorca give nearly 100 per cent black heads. Black is dominant, but imperfectly so; the nega- tive characteristic is recessive. The dominant character is less perfectly dominant in the female sex than in the male. COLOR OF HACKLES—HACKLE I,ACING. The color of the hackle feathers and the correlated saddle feathers in birds of broken color usually differs from that of the rest of the plumage. This peculiarity of the hackle coloration is an old character, since it is exhibited by the Jungle fowl, and was probably in the ancestor of the Aseel-Malay group. The feathers are laced with a lighter color than the center. In crosses between Minorca and Dark Brahma, and White Leghorn and Dark Brahma the solid color (black or white), the new, positive character- istic, dominates over the lacing. Nevertheless, in the Minorca X Dark Brahma hybrids the feathers of the nape are frequently faintly laced with gray. The black is imperfectly dominant. WING COLOR—RED WING COVERTS. The male Jungle fowl has red on the upper wing coverts, aud doubtless the male of the ancestors of the Aseel-Malay group had also. The male hybrids between the Dark Brahma and the Black Minorca on the one hand and the White Leghorn on the other usually show red on the wing coverts, although there is no other red in the plumage. Red on the wing coverts is probably dominant, but it is much reduced. TAIL COLOR. Although the tail feathers are derived from a distinct feather tract, and in broken-colored birds are usually without the red of the wing, yet tail color does not seem to be a unit character ; in inheritance it follows the rest of the body plumage. On the other hand, in breeding buff varieties black persists in the tail feathers longer than in the others. This case resembles the per- sistence of black at the extremities of the legs of white or red rabbits (Castle, 1905). SHAFTING. The female Jungle fowl has a light shaft to the feather. The same is true of the Tosa fowl and some Games. Light shafting is a primitive characteristic of the female. In the female hybrids between the Tosa fowl and White Cochin the shaft- ing is greatly broadened, and this is the principal modification of the plumage color. In female hybrids of the Tosa fowl and Dark Brahmas the shafting of the feathers of the back and wing coverts is striking, and some shafting appears in two of the males, probably transferred from the female (p. 54). Apparently shafting is dominant. 78 INHERITANCE IN POULTRY. BODY LACING. This character is not found in the Jungle fowl, but may have been derived from the penciling of the Aseel-Malay group. In male hybrids between the Tosa fowl and the Dark Brahma it occurs, derived from the latter (p. 54). It appears to be dominant. PENCILING. This is an ancient feminine characteristic, best marked in the Aseel-Indian group (p. 53). It is found particularly well developed in the Dark Brahma female. Inthe female hybrids between that race and the Tosa fowl penciling is well developed ; it is dominant. GENERAL TOPICS IN INHERITANCE. UNIT CHARACTERS. Taxonomic descriptions of plants and animals give a list of their specific characteristics (Merkmale, caractéres). These comprise for the most part only the external characteristics, but a similar list might be made for internal characteristics. In addition to specific characteristics, those of a higher order (such as generic, etc.) and those of a lower order (such as varietal) may be enumerated. Such characteristics are, in first approximation, unit char- acters. They are of prime importance, because the whole problem of evolution is that of the origin and significance of the various unit characters of the body. The theory of the unit character is associated with that of its bearer in inheritance. Darwin (1876) and later de Vries (1889) designated as such bearers particles of the nuclear material named ‘‘pangenes.’’ ‘‘ Changed numerical relation of pangenes is the basis of fluctuating variability; dis- placement (Umlagerung) of pangenes in the nucleus conditions retrogressive and degressive mutations ; while the formation of new kinds of pangenes is necessary to the explanation of progressive mutations’’ (7. ¢., those exhibit- ing altogether new characteristics). The two main hypotheses of the origin of unit character are that of de Vries and that of Weismann. De Vries sets forth his hypothesis at the very begin- ning of his great work, ‘‘ Die Mutationstheorie.’’ His words may be thus translated : As mutation theory I designate the doctrine that the characteristics of organisms are built up of units that are sharply separable one from another. These units can be united into groups, and in related species the same units and groups recur. Transitions, such as the external forms of plants and animals exhibit in such numbers, exist between the units as littleas between the molecules of chemistry. .... In the realm of the doctrine of descent this principle leads to the conviction that species have proceeded from one another not continuously but by steps [nicht fliessend, aber stufeuweise]. Each new unit added to the older ones constitutes a step and separates the new form, as an independent species, sharply and fully from the species whence it arose. .... Die neue Art ist somit mit eiuem Male da; sie entsteht aus der friiheren ohne sichtbare Vorbereitung, ohne Ubergange. GENERAL TOPICS IN INHERITANCE. 79 Weismann, on the other hand, is only less clear in expressing his hypoth - esis. He accepts, of course, the idea of unit characters, each of which is rep- resented in the germcells by a ‘‘determinant.’’ ‘‘ We called,’’ hesays (1904, I, p. 369), ‘‘ determinants those parts of the germ-substance which determine an ‘hereditary character’ of the body ; that is, whose presence in the germ determines that a particular part of the body, whether it consists of a group of cells, a single cell, or a part of a cell, shall develop in a specific manner, and whose variations cause the variations of these particnlar parts alone.’” The ‘‘ hereditary parts’’ may be small or ‘‘large regions, whole cell masses of the body, which in all probability vary only ez d/oc, as, for instance, the milliards of blood cells in man, the hundreds of thousands or millions of cells in the liver and other glandular organs, the thousands of fibers in a muscle, or of the sinews or fascia, the cells of a cartilage or a bone, and soon. In all these cases a single determinant, or at least a few in the germ plasm, may be enough.’”’ For Weismann (1904, II, p. 151) the ultimate source of all hereditary variations is the variation of the representatives of the unit char- acters in the germ plasm. ‘‘If I mistake not,’’ he says, ‘‘ we may at least say so much, that all variations are, in ultimate instance, quantitative and that they depend on the increase or decrease of the vital particles, or their constituents, the molecules. .... What appears to us a qualitative varia- tion is, in reality, nothing more than a greater or less different mingling of the constituents which make up the higher unit; an unequal increase or decrease of these constituents, the lower units.’’ The cell changes its consti- tution when the proportion of its component parts ‘‘is disturbed, when, for instance, the red pigment granules which were formerly present, but scarcely visible, increase so that the cell looks red. If there had previously been no red granules present, they might have arisen through the breaking up of certain other particles—of protoplasm, for instance, in the course of metab- olism —so that, among other substances, red granules of uric acid or some other red stuff were produced. In this case, also, the qualitative change would depend on an increase or decrease of certain simpler molecules and atoms constituting the protoplasm-molecule.’’ In criticism of the foregoing it may be said that a variation in the number of atoms in a protoplasmic molecule is certainly also a qualitative change— a mutation. The only real difference between Weismann and de Vries depends on the extent of the mutative modification, whether progressive or complete from the beginning; but this is a real difference, for the latter view is required by the theory of immutable unit characters. The former view is not in harmony with sucha theory. Conversely, if it appears that there are immutable unit characters, then the theory of evolution by saltation is necessary ; if unit characters are modifiable, then species may have arisen gradually. 80 INHERITANCE IN POULTRY. The result of the breeding experiments described herein bears upon this discussion. No other group, I imagine, exhibits so many characteristics as poultry ; of the comb alone there are half a dozen forms. The forms of feathers and their color patterns are numerous. These forms are sharply marked off from one another for the most part ; moreover, when two char- acteristics are crossed the result is rarely a blend. ‘This was a great surprise to me, as I had anticipated that blends would be the rule ; and, overwhelmed by the facts, I embraced at once the theory of immutable characteristics. That there are unit characters in poultry can not be doubted. When single and V comb are crossed and progeny obtained all with a Y comb, how con- vincingly do the second hybrids reproduce the single comb in some individuals and the Y comb in others! Though the cerebral hernia and its associated great crest may disappear in the first generation of hybrids, how beautifully do they reappear in one-fourth of the offspring of such hybrids! How in- structive is it to see perfectly plain feathered offspring arising from a frizzled pair, or in a Black Minorca X Dark Brahma white-laced hackles appearing in an otherwise dead-black plumage! Truly we may hope, as in chemistry, to make various kinds of molecules by the proper admixture of our atoms— the characteristics. Even in man such non-blending characteristics are evi- dent. One of the most famous is the Hapsburg lip or chin, which from the fifteenth century has persisted to the present day despite infusion of new blood during fifteen generations.* Another striking case is that of hypo- phalangia in man, described by Farabee (1905). In the four or five gener- ations studied, there has, he states, ‘‘never been a single instance of partial inheritance, but in all cases all extremities have been affected in precisely the same way.’’ While admitting, thus, the reality of unit characters, the further study of the evidence of hybridization in poultry has led me away from the conception that they are rigid and immutable as atoms are, which may be combined and recombined in various way and always come out of the process in their pristine purity. This is by no means the case. Very frequently, if not always, the character that has been once crossed has been affected by its opposite with which it was mated and whose place it has taken in the hybrid. It may be extracted therefrom to use in a new combination, but it will be found to be altered. This we have seen to be true for almost every char- acteristic sufficiently studied—for the comb form, the nostril form, cerebral hernia, crest, muff, tail length, vulture hock, foot-feathering, foot color, ear- lobe, and both general and special plumage color. Everywhere unit char- acters are changed by hybridizing. How does this fact bear on the rival theories of evolution? It has an im- portant bearing onthem. It is notin accord with the statements of de Vries * Cf. F. A. Woods, 1902-03. GENERAL, TOPICS IN INHERITANCE. Sr quoted above: ‘‘ The characteristics of organisms are built up of units that are sharply separable one from another,’’ and ‘‘ Transitions exist between the unit as little as between the molecules.’’ Single comb is one unit and pea comb is a different unit, but they are not sharply separable. Crest and no crest are units, but they run into each other in hybridizing. Unit char- acters may show transitions, and, if so, they may have originated gradually, so far asIsee. It does not follow that they must have originated gradually. ALTERNATIVE, PARTICULATE (MOSAIC), AND BLENDING INHERITANCE. Doubtless Darwin’s statement that crossed characters usually blend is still the prevalent view. Much if not most biometric work in heredity has been made on this basal assumption. I may say that I began my experi- ments prejudiced in favor of this view. The results that have been recorded in the foregoing pages indicate that probably in general typical blending of characters is rare. Excepting char- acters like general form of the body, which are doubtless not units, but complex, I have, indeed, seen no single case of a typical blend. A fusion of characters is a rather rare phenomenon. Human skin color is the one striking case. One can but wish we had more careful data on inheritance of human skin color in successive generations. Other human characteristics show alternative inheritance. ‘This is strikingly true in Farabee’s family of hypodactyls cited above. It is said to be true of eye color and probably of the states of general pigmentation known as blonde and brunette. The following characters of poultry show alternative inheritance : Comb form. Uropygium. Earlobe color. Nostril form. Tail length. General plumage color Cerebral hernia. Vulture hock. (sometimes). Crest. Booting. Color of hackles. Muff. Extra toe. Wing bar. Beard. Color of mandible Shafting. Frizzling. and foot. Body lacing. Silkiness. Iris color. Penciling. The following characteristics show particulate inheritance : Iris color (sometimes ?). White and black, producing darving (Series VI, VII, IX, XII). White and black, producing blue (fig. 54) (a fine mosaic of white and black). It is too early yet to interpret the cases of particulate inheritance. It isa striking fact that, excepting the Tosa * White Cochin cross, all my barred birds reared to maturity had the White Leghorn Bantams as mother or father. Now, as repeatedly observed, these bantams were heterogametous. It is possible that they contain barred blood in the “‘fixed”’ condition. Aside from the fact that they throw a certain proportion of barred birds, this conclusion gains support from the fact that the wing coverts of the male are 6 82 INHERITANCE IN POULTRY. obscurely barred with dusty bands, although, on the other hand, this barring may be merely the badge of heterozygotism. It is possible, therefore, that the barring in the plumage of the White Leghorn Bantams is transmitted as an alternative characteristic. The case of the barred descendants of the Tosa X White Cochin is more difficult. I am not yet prepared to go so far as Correns (1905", p. 13, note) when he says: ‘‘ Wo Mosaikbildung als Regel bei einem Bastard auftritt, war sie schon in einem der Eltern oder in beiden, aktiv oder latent, vorhanden.’’ Naturally, attention was directed chiefly toward evident qualitatively marked characteristics. Such do not blend. The fact that for the most part a characteristic does not blend when crossed with its allelomorph is of the highest importance for the theory of evolution. If blending were uni- versal a new characteristic must inevitably become quickly swamped by intercrossing with the parental characteristic. Since the new quality does not blend, it need not be swamped, even when there is no special isolation. INHERITANCE OF SPECIFIC VS. VARIETAL CHARACTERISTICS. A distinction between specific and varietal characteristics is made by Nageli (1884, p. 247) and by de Vries (1902, p. 141; 1905, p. 141). Fol- lowing de Vries, a specific characteristic is a wholly novel one acquired by the race—one which stamps its possessor as an elementary species. A varietal characteristic is sometimes positive (7. ¢., additional), in which case it is found also in closely allied species, and may be regarded as the becoming patent of a characteristic all the time latent in the variety. It is, on the other hand, sometimes negative, this condition being marked by the disap- pearance (becoming latent) of a characteristic patent in the ancestral species. Specific and varietal characteristics are thought by de Vries to be inherited very differently. When two elementary species are crossed the character- istics of both parents appear, fully developed, side by side ; Mendel’s law is not followed. When a species is crossed with a variety a Mendelian result is obtained and the patent characteristic is dominant over the latent. Let us now see in how far the results gained in breeding poultry accord with de Vries’s law. It is not easy to make the classification in an unpreju- diced way ; an attempt, however, will be made. First, the comb is a specific characteristic of the genus Ga//us. It is absent in other Gallinee. Also pea comb and rose comb are each wholly new, posi- tive variations from the primitive single comb. Muff and beard seem to be novel ; so also the long tail of the Tosa fowl, the extra toe, and the melanic feet and beak. Clear cases of negative variations are: Loss of the nasal process of inter- maxillary and consequent igh nostril, failure of cerebral plate to close and consequent cerebral hernia ; loss of uropygium ; loss of red and black pig- ment in feathers (albinism, partial or complete) ; loss of dark pigment in crest feathers ; loss of wing bar ; loss of primitive shafting. GENERAL TOPICS IN INHERITANCE. 83 Now, by hypothesis we should expect a difference in inheritance in these characteristics as indicated below : Expected non-Mendelian. Expected Mendelian. . High nostril vs. low. . Cerebral hernia vs. normal. . Taillessness vs. normal tail. Albinism in plumage vs. pigment. Absence of wing bar vs. presence. . Absence of shafting vs. presence. Pea and rose comb vs. single comb. Muff and beard vs. plain head. Long tail vs. normal. Extra toe vs. normal. Melanic feet and beak vs. willow or yellow. SESS fe DPW nH Of the five cases where, on de Vries’s theory, we should expect non-Men- delian results, No. 4 is apparently not Mendelian, No. 5 gives often a mixture of characters, Nos. 1 and 2 apparently give true Mendelian domi- nance and recessiveness, No. 3 is still doubtful. Of the six cases in which a Mendelian inheritance is looked for, we certainly find it in three cases and less certainly in the others. On the whole, there is a slight but not a striking difference in transmission between the two sets of characteristics, and I can only conclude that for poultry, so far as I can see at present, de Vries’s formula does not hold universally. INHERITANCE OF POSITIVE VS. NEGATIVE VARIETAL, CHARACTERISTICS. According to de Vries, when an individual having a certain characteristic patent is crossed with one in which it is latent the patent characteristic is dominant, the latent recessive. Do results with poultry confirm this law ? In the following table the patent characteristic is given in the left-hand column and the dominant characteristic in zfa/ics - | Patent. Latent. | 1. Nasal process of premaxillary, zarrow | High nostril. nostril, 2. Closure of cerebrum completed ; plain | Failure of cerebrum to close; cerebral | head. hernia. 3. Crest; black crest feathers...........- Smooth head ; white crest feathers. 4. Complete development of the feather..| Interrupted development of the feather ; | silky feather. Ba A ae aod agenene <> SER oS .. .. | Taillessness. 6. Pigmented plumage ................ Albinism in plumage. Gh, HAE COG WAS 6 006 oba880 aA JooEa0 Uniformly colored wing. 8 b SAU IIa gancdanooSneda oda boc .....| Plain feather. Of the foregoing eight characters, seven clearly follow the law that patent characteristics dominate over latent. No. 6 isa clear exception, for since all the wild Gallinze are deeply pigmented birds it can hardly be doubted that white is a negative variation in which color is latent. However, the exception (No. 6) is not universal, for white plumage does not always domi- 84 INHERITANCE IN POULTRY. nate over pigmented plumage. It appears, then, that the patent character is, in general, but with some exceptions, dominant over the corresponding latent character. INHERITANCE OF OLD VS. NEW CHARACTERISTICS. Standfuss (1896, p. 111), asa result of his hybridization of moths, concluded that hybrids resemble the older species. De Vries (1902, pp. 33-42, and 1905, pp. 280, 281) cites several instances of the prepotency of the phyloge- netically older characteristic. Bateson and Saunders (1902, p. 137), how- ever, point out that younger characteristics sometimes dominate, and cite pea and rose comb, extra toe, and the polled condition of cattle as examples. Correns (1905, p. 463 et seq.) describes a case of petaloid calyx—a new characteristic—which is dominant over the normal form. Correns’ (1905°, p. 13), indeed, concludes that in general the phylogenetically more advanced characteristic—the later originated, younger characteristic—dominates. Let us see what evidence poultry hybrids have to offer bearing on this point. | | Old characteristics. |New characteristics. | Old characteristics. | New characteristics. | I. Single comb.....) Rose comb. 11. White skin.....| Black skin. 2, IEG) POs wee | High nostril. inn2teRedittistme seis Black tris. 3. No hernia... .. | Hernia. | 13. Red earlobe....| White earlobe. 4. Plaintheada-ane: | Crest. || 14 Pigmented. White (sometimes 5. No muffling..... Mufiling. ] dominates). 6. Plain feathers...| Mrizzled feathers. || 15. Red pigmented.) Black ; no red. | 7. Plain feathers..., Silky feathers. |, 16. Black head.....| White head. Sh IRE s ns aoos Non-tailed. 17. Hackle lacing. .| Solid black. g. Tail feathers lim-)| 7az/ unlimited. | 18, Red wing bar..| No wing bar. ited in growth. | || 19. Shafting...... | No shafting. TON Fouritoesi ya. c- Five toes. | 20. Penciling ......| No penciling. | } This table shows that of nineteen characteristics (No. 10 being left out of consideration), nine old ones are dominant and ten newones. Clearly, dom- inance of characteristics in poultry is not determined by the age of the characteristic. DOMINANCE AND RECESSIVENESS. Mendelian dominance and recessiveness with segregation of characteristics in the gametes are not universal concomitants of hybridization. Mendel knew it (Correns, 1905*) ; de Vries founds his system on the fact ; Correns lays stress on it; Bateson and Saunders (1902, p. 152) recognize it, but consider the exceptions insufficiently known. The characteristics that I have crossed show always segregation excepting extra toe and perhaps also melanic foot and beak color. ‘These are among the positive variations of de Vries, which, in accordance with his system, we should not expect to ‘‘ mendelize.’’ As stated, other positive variations, however (pea comb and muff), seem to mendelize. GENERAL TOPICS IN INHERITANCE. 85 Of the varietal characteristics, the positive or patent characteristics almost always are dominant, white plumage forming an occasional exception. On the other hand, phylogen+tically old characters are not more apt to be domi- nant than “‘new’’ ones. Some evident sports, such as crest, frizzling of feathers, unlimited growth of tail, and black skin (of Silky), are dominant. Other sports—hernia, shortened premaxillary, silkiness, and rumplessness— are recessive ; the novelty or antiquity of the characteristic has nothing to do with its dominance. Dominanceof a character in hybridization is deter- mined by the same causes as determine the appearance in the race of a posi- tive variation. A progressive variation, one which means a further stage in ontogeny, will be dominant; a variation that is due to abbreviation of the ontogenetic process, which depends on something having dropped out, will be recessive. This conclusion, however satisfactory, must be regarded as tentative. It is doubtful if it is of general validity ; for while long tail and crest feathers are dominant in poultry, long hair (equally due to prolonged life of the fol- licle) is recessive in mammals (Castle, 1903 ; 1905, pp. 64-67, 73-74; Hurst, 1904). White is usually recessive to pigment in flowers and mammals, but it is usually dominant over pigment in poultry. It is still too early to regard the conclusions expressed in the last paragraph as anything but an hypothesis. While dominance and recessiveness are typically found in Mendelian in- heritance, yet they may be absent even in cases when segregation of charac- teristics occurs in the second hybrid generation. Thus, the barred offspring of the black-and-red Tosa fowl and the white Cochin throw in the F, gener- ation 25 per cent black and red and 25 per cent white, but the remainder, like all of F,, is barred with white, and no one can say which plumage color isdominant. ‘The same is true of some black-and-white barred hybrids. It is also true of hybrids between single and Ycomb. ‘The phenomena of domi- nance and recessiveness do not always accompany segregation. Another modification of the law of dominance and recessiveness must be recognized, namely, that they are by no means always complete. Even in the first hybrid generation the dominant characteristic is more or less inter- mediate. ‘The antagonistic characteristics a and a’ of the two parent types are not only united in the zygote, but they pass in the development of the or- ganism into all the tissues of the body, and particularly into the cells out of which the organ 4 is developed. The dominant characteristic, a, and the recessive characteristic, a’, each works to determine the quality of the organ 4. If a dominates, it is because it is more active than a’. It does not dominate by excluding a’. Sometimes, as in the case of barred feathers, it appears that a and a’ in ontogeny alternate in their activities. The cells of acertain zone of the feather manufacture only black pigment ; in the next zone black is wanting ; then comes a zone of black, and so on, in many repe- titions. Dominance as contrasted with recessiveness is a matter of degree and not of kind. ) 86 INHERITANCE IN POULTRY. Various authors refer to the imperfection of the dominant or recessive characteristic in the hybrid. Bateson and Saunders (1902, p. 23) say: Although the offspring resulting from a cross between any two of the forms (of Dadura) employed is usually indistinguishable from the type which is dominant as regards the particular character crossed, yet in other cases the intensity of a dominant character may be more or less diminished either in particular individuals or in particular parts of one individual. Hurst (1905, pp. 145-154) records many cases of imperfect dominance in poultry and estimates the incomplete dominants to be twice as numerous as the complete dominants. DEPENDENCE OF DOMINANCE ON THE RACES CROSSED. Is one of a pair of allelomorphs that shows itself dominant when varieties A and & are crossed likewise dominant when any other varieties, J7 and J, are crossed, or is the relative potency of the allelomorphs dependent upon the varieties in which they happen to reside? Data for an answer to this question are to be found in the experiments where the same pair of allelomorphs were crossed, using different varieties. We may except from this list the Minorca x Polishand the Leghorn x Houdan crosses, as the races involved are very closely related. The following allelomorphs remain for consideration : (1) Crest vs. crestlessness. (6) Extra vs. normal toes. (2) Silkiness vs. non-silkiness. (7) Black vs. white skin. (3) Rumplessness vs. tail. (8) Black vs. yellow beak. (9) (4) Vulture hock vs. plain hock. White ws. dark plumage. (5) Boot vs. clean foot. Crest.—This is dominant when Polish or Houdan is crossed with the Mediterranean breeds and when the Silky is crossed with the Frizzle or with the Jungle fowl. Crest is uniformly dominant over crestlessness, no matter which of these races are used. Silkiness is recessive to non-silkiness when crossed with Frizzle or the Jungle fowl. Non-silkiness is probably always dominant. Rumplessness in a Game fowl was recessive to the tailed condition of Leg- horn, Cochin, Frizzle, and Nankin. The tailed condition seems always to dominate. Vulture hock is recessive when an Asiatic race is crossed with any Med- iterranean breed or a Game, and probably, in general, plain hock dominates. Booting is dominant when the booted form is the mother, no matter what the race. Booting is much reduced and sometimes altogether absent in the first generation of hybrids when it is derived from the father. Inheritance of booting is independent of race but not of sex (p. 38). Extra toe seems not to Mendelize. The excess of extra toes in the first hybrid generation holds for all the races crossed and is probably independent of race. GENERAL TOPICS IN INHERITANCE. 87 Black skin of the Silky dominates over the colorless skin of the Frizzle and of the Jungle. It probably dominates throughout. Yellow vs. black beak and foot coloy.—Yellow of the White Leghorn domi- nates over black of the Minorca, but yellow of the Dark Brahma is domi- nated by the Minorca. Here yellow behaves differently, according as it is in the Leghorn or Dark Brahma race. It is quite possible that the yellow is not identical in the two groups, but that, while it is ancestral in the Dark Brahma, it is secondary and a progressive character in the Leghorn. ‘The lack of uniformity in dominance of yellow may be due to essential dissimi- larity of the character in different races. White vs. dark plumage.—Aside from cases of barring and Andalusian coloration, white usually dominates over dark plumage. This is true in all cases where White Leghorn is employed as white race, whether the other race is Game, Dark Brahma, Houdan, or Minorca. When the Silky is used as the white race white is sometimes recessive (fig. 53), but it must be ac- knowledged that the dark parents were not the same as were used with the Leghorn, but were a Game, Frizzle, and Jungle fowl; consequently the results in the two series are not strictly comparable. However, Darwin found the white of the Silky recessive to the black of the Minorca. It is hardly conceivable that the white of the Silky is different from that of the Leghorn; soit must be concluded that white inherited as a solid color is sometimes dominant and sometimes recessive, depending on the race in which it inheres. Summarizing the foregoing evidence, it appears, first, that (except in certain obviously complex color characters) when one of a pair of allelo- morphs is dominant it is so regardless of the races crossed. This shows that dominance and recessiveness depend upon a relation of the character- istics fer se and not upon any relation of the races into which they have been introduced. This is in accord with the conclusion reached above, that dominance is determined by the fositive nature of the characteristic (p. 84). PREPOTENCY AND DOMINANCE. Prepotency was a much used and probably abused term in the period pre- ceding the revival of Mendelism. In the new era all of the old terms have been subjected to reexamination as to their significance. Bateson and Saun- ders (1902, p. 121) use the term ‘‘as signifying determination of dominance,’’ z. €., whether the normally dominant or the normally recessive character shall be in any case actually dominant. Castle (1905, pp. 58-64) shows that although rough coat is dominant over smooth coat, a few smooth-coated mothers will, when crossed with rough males, produce partial-rough young. The normally recessive character here partially dominates. In my own experiments the most remarkable case of dominance is exhibited by a gamete from the maternal side that produced the Houdan ~ White Leghorn hybrid 88 INHERITANCE IN POULTRY. No. 386 9 ; for this hybrid has a high nostril and a pair of papillee like the Houdan mother, both of which characters are recessive. Out of 41 in- dividuals No. 386 is the only one that exhibits them. It appears, then, that ‘“ prepotency ’’ in its modern sense can not be neglected. HYBRID FORMS. It sometimes happens when two dissimilar characteristics are crossed that neither appears in the offspring, but they are replaced by a new character. This fact has been long known. Mendel obtained such hybrid forms (¢/., Correns, 1905, p. 232). Several cases are cited by Focke (1881, pp. 473, 474). He refers particularly to the blue hybrid of the white Datura ferox crossed with the likewise white D. /aevis and D. strammonium Bertolonit. As a result of more recent work it appears probable that hybrid forms are of two kinds. First, such as are atavistic or due to the becoming patent of a latent characteristic ;* and, second, such as are due to a particulate inher- itance of the two characteristics crossed. In the latter case all that is novel in the hybrid is the replacement of either szzg/e character by a combination of characteristics. Atavistic hybrid forms have been carefully investigated of late, especially by Correns (1902) and Cuénot (1903), who have applied a method of inter- pretation to particular cases. When albino mice are crossed inéer se they produce only albinos. But if such an albino is crossed with a pigmented (e. g., a black) mouse its latent pigment appears and the offspring may be all gray, or perhaps yellow and gray or yellow and black. The same holds exactly true for albino rabbits, as Hurst (1905, pp. 306-310) has shown. Cuénot’s interpretation depends on the principle that pigments result from the action of an oxidizing diastase (tryosinase) upon a chromogenic sub- stance. Both of these elements are present in a pigmented mouse, but he assumes the chromogenic substance alone is presentinthealbino. The sperm from the pigmented male brings to the egg of an albino the diastase necessary to the production of pigment in the offspring. Correns (1905°) finds that the hybrid of Mirabilis jalapa alba (white flowers) and JV/. jalapa gilva (yel- low flowers) has rose-colored flowers that are, moreover, sfv7fed with red. His experiments lead to the conclusion that the a/éa variety forms no pig- ment, but does produce a pigment-changing (reddening) enzyme. The gi/va variety forms pigment, but not the reddening enzyme. When al/éa sperm unites with the g7/va egg the pigment of the latter, under the influence of the reddening enzyme, becomes rose. Similarly with striping. ‘There is evidence that this is only partly latent in a/ba and completely latent in g7/va. Now if we assume a factor that permits the development of the striping determinant to be active in g7z/va but to be latent in a/éa, the imperfect * Tschermak (1904, p. 95) would add as another kind that in which an originally patent character becomes latent. GENERAL TOPICS IN INHERITANCE. 89 development in a/éa of the striping determinant is accounted for. When the sperm of g7/va, bringing the active principle for striping, fertilizes the ege of alba with its striping determinant, the striping makes its full appearance. These two or three examples from both plant and animals indicate a method of explaining hybrid forms that is probably of wide applicability. Are the hybrid forms of poultry to be explained on the atavistic or the particulate inheritance theory? ‘Take first the case of barring. Three tests can be applied: First, inherent probability from the ancestry of the fowl crossed ; second, general distribution of barring among the offspring ; third, proportion of different forms of plumage pattern in generations beyond the first. The cross between Tosa fowl and White Cochin gave barred birds. If the barring were latent it must have lain in the Cochins—the form without visible pattern. It is fairly certain that neither of the ancestors of domestic fowl was barred ; hence if the barring determinant existed in the Cochin bantam it must have been introduced by a recent cross. Bantamizing of Cochins is effected by crossing with some bantam race, but until recently no barred bantams have been created. It is therefore highly improbable that a barred bird was used to bantamize the Cochins. While it is possible, it is improbable that the White Cochin contained a barred determinant. Second, barred vaces have the two sexes equally barred, but our hybrids are barred inthe male only ; consequently barring here acts like a neomorph. Third, on the theory of atavism we should expect to get in the second hybrid generation : | Coloration of second generation. oe | Paeenae | Actual. 3 | J | Per cent, Per cent. Per cent. IW CO RM race step terrietetelicelalaveteioiste siscelelsis | 25.00 | 25 28 Pigmented and barred............. 56 25 50 48 Pigmented and not barred......... | 18.75 | 25 24 | The actual proportions of the three types accord much better with the particulate inheritance theory than with that of atavism, but the total number of offspring is insufficient to givecertainty. It may be concluded that while the evidence does not exclude the atavism theory of the cropping out of barring, it favors the theory of particulate inheritance. The case of the hybrid between single and Y comb rests on more extensive data. ‘These are set forth on pages 10-12, and are less favorable to the ata- vistic theory than to the particulate theory. The other heterozygous forms have been less carefully studied. ‘Theyare the blue, Andalusian (fig. 54, pl. xvi1), plumage color resulting from a white and a black crossed, and the case of the down of the hybrid Minorca Dark Brahma chicks. This is black like the Minorca, but lacks the white of the chicks both of that race and of the Dark Brahma. ‘The Andalusian gO INHERITANCE IN POULTRY. breed has been discussed by Bateson and Punnett (1905, p. 126), and they find, what is the universal testimony of breeders, that (as stated also at page 76) the blues bred infer se produce some white and some blacks, but still more blues. Until more complete statistics have been gained on the pro- portions of colors in the offspring, the interpretation of blue must remain uncertain. Hybrid forms are, then, frequently cases of particulate inheritance in which the hybrid gametes are not mosaic ; consequently whenever ‘“‘ pure”’ offspring are produced, as in F,, these reassume the character of the pure race. In some cases, as in the cuckoo Dorking and the Dominique (from which our barred Plymouth Rock has been derived), the heterozygous form of barred plumage has become fixed, so that only barred offspring are pro- duced. A mosaic gamete has been created. The blue coloration has never yet been fixed as a permanent hybrid form. The method of fixing a hybrid form is urgently in need of investigation. REVERSION. This term has been used rather loosely in the past for the appearance in hybrids of characteristics not visible in the immediate parents of the hybrids and often belonging to remote ancestors. Darwin (1876) made much use of this term in describing his results. He believed that the occurrence of ‘“reversion’’ gave a useful key to ancestry. It is worth while to consider his observations and experiments. He mentions the fact that ‘‘ purely bred Game, Malay, Cochin,Dorking, Bantam,and..... Silk fowls may fre- quently or occasionally be met with, which are almost identical in plumage with the wild G. dankiva.’’ But does this indicate anything else than that this type of coloration has persisted in certain primitive races, like the Game, and has been transplanted from them to the new races? Darwin crossed a black Spanish cock with various white and white-and-black hens of pure breed. The offspring of this cock crossed with a silver-spangled Polish hen and with a white Cochin hen showed no sign of reversion to the red color of G. bankiva. The male offspring of a spangled or silver Hamburgh hen showed white in the hackles and a reddish yellow on the saddle. Darwin regarded this asa ‘‘ first sympton of reversion ;’’ but in the first of these peculiarities the hybrid resembles G. danxkiva less than the Dark Brahma. The offspring of a white Game hen with the Spanish cock was at first snow white, but eventually produced the ‘‘pile’’ coloration. Darwin regards this as a partial reversion to G. dankiva ; but it is equally possible that the reversion is only to a pile coloration that is latent in the white from an earlier cross and is brought out when the white is crossed with a dark color. But Darwin’s most remarkable hybrid was the offspring of a white Silky hen. Of two cockerels one was black (with light laced hackles) ; the other resem- bled closely a Jungle cock. Darwin admits that the case is extraordinary, GENERAL TOPICS IN INHERITANCE. gti but it was duplicated by Mr. Tegetmeier. This experiment certainly should be repeated, and I have arranged to repeat it next season. One of the best cases of reversion is the gray coat of a hybrid between a white and a black mouse. We now know, however, that even a ‘‘ pure race’’ of white mice may carry gray as a latent characteristic that first be- comes patent on crossing. In view of such facts cases of ‘‘reversion’’ toa remote ancestor must be critically examined. If the ‘‘reversion’’ be not a neomorph, it must have been handed down without break in the germ plasm from an ancestor possessing the characteristic. PURITY OF GAMETES. The dogma of purity of the gametes, the second corner-stone of Mendelism, asserts that while the unripe germ cells of a hybrid having antagonistic or alternative characteristics 4 and 4’ contain representatives of both 4 and A’, yet the vife germ cells of such a hybrid contain representatives of either A or 4’, and not of both. Thus the ripe germ cells (gametes) are pure in respect to a given characteristic. They gain this purity, it is supposed, dur- ing the maturation period, the period when the reduction division of the chromosomes occurs, and when in each cell division one-half of each chro- mosome moves bodily to one daughter cell and one-half to the other. The theory assumes, of course, that characteristics 4 and A’, being derived from different parents, inhere in different chromosomes. Let us assume that our hybrid has eight chromosomes, four derived from each parent, thus: zo) 16) 2 & °o @ in which the black dots represent chromosomes of maternal origin; the circles chromosomes of paternal origin. If all maternal chromosomes contain the determinant @ then purity of the gametes demands that all such go to one gamete and all of the chromosomes of paternal origin go to the other, and that such is their behavior has in fact been assumed by Cannon (1902). But that would result in the extracted pure individuals of the second hybrid generation being like their grandmother or their grandfather in all charac- teristics, which is not the case. If we assume that some only of the maternal chromosomes, such as are represented by the small dots, contain the deter- minant a, then these may be associated with any of the paternal chromo- somes excepting those that contain the determinant a’. Such a selection of chromosomes so as to exclude from the ripe gamete chromosomes containing both the alternative characteristics is quite possible, owing to the fact of synapsis, in which the omologous chromosomes from the two parents unite in pairs, as shown in the figure, in such a way that both can not pass to the same gamete. The foregoing hypothesis of Sutton (1902, 1903) and Boveri (1902) would account for perfect purity of gametes. But it is clear that gametes are not g2 INHERITANCE IN POULTRY. wholly pure, since the characteristics in second generation hybrids are rarely exactly like those of their grandparents ; consequently various additional hypotheses have been offered accounting for this feature. Hacker (1904) points out that chromosomes do not pass from cell to cell unchanged except for their growth and division. During the resting stage ‘‘of the nucleus it disappears. The new nucleus which arises in the position of the old is at first small; it arises inside of the old chromosome as a spore arises in the mother cell; its material has been derived from a part only of that of the mother chromosome; the remainder goes to form part of the cytoplasm. Though chromosomes from different parents tend to separate to distinct gametes, still all gametes are infected by each kind of characteristic.”’ McClung (1995, p. 329) assumes, more vaguely, a mutual influence of synap- tically paired chromosomes in the prophase of the first spermatocyte. A different suggestion is offered by Ziegler (1905). He assumes that each chromosome of maternal or of paternal origin carries determinants of a// characteristics. After maturation all gametes contain the same number of chromosomes, but the proportion in them of chromosomes of paternal and of maternal origin varies. Gametes rarely contain exclusively maternal or paternal chromosomes, but whenever the proportion from one parent is high the gamete acts as though it contains exclusively the gametes of that one ancestor. If two gametes that are prevailingly paternal unite in a zygote the resulting hybrids (of the second generation) show all the grand-paternal characteristics. The difficulty with this hypothesis is that, like Cannon’s, it does not account (any better than the first hypothesis) for the diverse combinations of characteristics shown in the second hybrid generation. Still another suggestion has been made by Morgan (1905). It is that the gametes are not pure, but contain determinants of both allelomorphs a and a’, and that one of these dominates in half of the gametes and the other in the remaining half. The advantage of this hypothesis is that it accounts for latent dominant characters in recessive individuals. This hypothesis assumes that the gametes of hybrids are always impure, and that this im- purity can not be got ridof. This seems to me to be contrary to experience. Moreover, except for the explanation that it offers of latency—which has been accounted for on other grounds by Cuénot—it offers no practical advan- tage over the theory of pure gametes. From the foregoing diversity of hypotheses it is evident that we lack a fully satisfactory cytological explanation of the facts other than that of purity— the fact of imperfect dominance and the fact of particulate inheritance com- bined with purity in the second hybrid generation. Perhaps it will suffice to suppose a restricted purity of gametes such that the determinant of a characteristic may become infected to a slight degree by the presence of its allelomorph. GENERAL TOPICS IN INHERITANCE. 93 COMPARISON OF RECIPROCAL CROSSES. There is a notion among breeders of poultry that the father and the mother contribute different qualities to the offspring ; and if the cytoplasm carries any hereditary tendencies this result is to be expected, for the female trans- mits more cytoplasm than the male. Certainly the hybrid between a large hen and a bantam cock starts life on a very different plane of size from the hybrid between a bantam hen and a large cock. A writer in Wright’s Poultry Book (1902) says in respect to breeding Houdans that the male bird is more responsible for the outside qualities—color, size of crest, beard, tail carriage, color of legs, and so on. The hen determines laying qualities and general size. I have made only one extensive experiment on this matter. I crossed a single-comb White Leghorn bantam and a Dark Brahma both ways. The offspring of the Dark Brahma hen (weight, 1,300 grams) are a little heavier than those of the White Leghorn bantam hen (weight, 700 grams). ‘Two males descended from the one and the other mother, respectively, weighed at 3% months 720 and 550 grams. ‘The average of three pullets from the Dark Brahma at 3 months 22 days is 655 grams; of three pullets from the White Leghorn at 3 months 23 days is 626 grams. ‘The proportional differ- ence in the weight of the young of about 3 to 4 months is less than that of their parents, but is in the same sense. The booting of the offspring of the White Leghorn hen is much reduced as compared with the booting of the offspring of the Dark Brahma hen, the father in the first cross not differing from the mother in the second cross in its heavy booting. In plumage color the 19 offspring of the White Leg- horn female were all white except four. Of the 19 offspring of the Dark Brahma female, only six were white, the others resembling the Dark Brahma. Thus we see that in these three characters of weight, booting, and plumage color the offspring tended to ‘‘ take after’’ the mother. INHERITANCE OF SEXUALLY DIMORPHIC CHARACTERISTICS AND SEXUAL DIMORPHISM IN THE HYBRIDS. Most species of vertebrates exhibit certain characteristics peculiar to one or the other sex, and it is well known that, for example, a female peculiarity can be transmitted through a son to a granddaughter. Thus the good milking quality of a cow is transmitted through her son to his daughters. Whenever femaleness crops out in the history of the germ plasm the good milking quality, or whatever other quality it may be, also appears. The inheritance of dimorphic characters is most strikingly seen in hybridization. Thus I crossed a male Tosa fowl (which has self-colored feathers) with a white Cochin.“ The male hybrids are barred with white, but the female hybrids closely resemble in color the female Tosa fowl in having white * See Series IX. O4 INHERITANCE IN POULTRY. shafting on the contour feathers, although the white shafting is much broadened. When the barred male and broad-shafted females of this first hybrid generation were crossed the pure plumage of the Tosa fowl tends to reappear. The males have contour feathers without white and with much red ; the females have the shafted feather without any red. With maleness or femaleness go the proper secondary attributes. What is true of the Tosa fowl is true generally, and there is much oppor- tunity to test this matter in poultry, for sexual dimorphism is widespread. In all ‘‘dark’’ or ‘‘partridge,’’ silvered, and golden races as found in Brahmas, Cochins, Wyandottes, Dorkings, Hamburghs, Games, and Oriental fowl, the plumage of the two sexes is conspicuously different ; and to pro- duce sexual dimorphism in a race that is without it the use of one male bird of a dimorphic race may suffice. Again, in the male, comb and wattles are generally larger than inthe female. The rose comb of the male becomes often a modified peacombin the female. The simple comb of the Minorca, Spanish, and Dorking fowl is erect in the male, drooping to one side (equally to the right and left side) in the female. The form of the hackle and saddle feathers constitutes one of the most constant differences between the two sexes. These are long, narrow, and pointed in the male ; short, broad, and rounded in the female. ‘The tail feathers differ similarly. ‘Thesickle feathers and those of the middle row especially continue to grow in the male long after their growth has ceased in the female. Similarly the crest feathers of Polish and Houdans grow longer in the male than in the female, but on account of their greater breadth in the female her crest appears larger and fuller. Lastly, the greater development of the spurs in the male over six to eight months old is a well-marked dimorphic character. Of these characters I have paid most attention to plumage and skin color, and will take up in review the results gained in crossing dimorphic species. Black Minorca and Dark Brahma.—The male Dark Brahma has white- laced hackles and black, white, and red wing bars. In the female the lacing on the hackles is less conspicuous, and there are no wing bars or bows. Red is wholly absent. All hybrids are prevailingly black. All males, how- ever, show a more or less prominent wing-bar formed of black, straw, and red colored feathers. No females show any trace of a wing bar unless it be a slight iridescence in the wing coverts. White Leghorn and Dark Brahma.—The male hybrids are typically white, with some red on wing coverts. Apart from some black individuals, the female hybrids are either white, with some buff on wing, or else they resem- ble the female Dark Brahma, having the penciling modified into mossiness. There is no well-defined wing-bar, but the middle wing is suffused with red. White Leghorn and Houdan.—Neither of these races exhibits a marked dimorphism in plumage color. Nevertheless, the coloration of the hybrids is dissimilar in the two sexes, the males being of a much purer white than GENERAL TOPICS IN INHERITANCE. 95 the females (p. 21), and this is true not only in the first generation, but also in the extracted whites of a later generation. White Leghorn and Rose-comb Black Minorca.—In the first generation the male hybrids were almost without exception pure white ; the female hybrids invariably show some black-speckled feathers. Tosa fowl and White Cochin Bantam.—In the first hybrid generation, as stated, the males had all feathers of male Tosa coloration, but barred with white. The females had the Tosa hen coloration, but with shafting broad- ened. Here each sex inherits the corresponding characteristic plumage of the Tosa fowl modified by the white of the Cochin, but zz different fashion for each sex. Barring or cuckoo marking seems, indeed, a prevailingly male characteristic. Hurst (1905, p. 133), in crosses of White Leghorn and Houdan, got, in addition to white hybrids, 11 dark birds; of these the 6 pullets were black ; the 5 cockerels were barred. In the F, generation I obtained extracted pure (?) male and female Tosa- fowl plumage as well as pure whites (p. 49). Dark Brahma (female) and Tosa fowl (male).— Here both races are dimorphic. The female hybrids closely resembled in coloration the female Tosa fowl, except that the contour feathers were penciled as in the Brahma. The male hybrids closely resembled in coloration the male Dark Brahma, except that much more red and less white appeared on the wing bars and wing bows. Both sexes inherit some qualities from the corresponding sex of each of the parent species. Again, the males have a yellow foot like their mother, whereas the females have a willow foot like their father. The hybrids of either sex inherit foot-color from the opposite sex of their parents (p. 54). TRANSFER OF SEXUALLY DIMORPHIC CHARACTEKRISTICS FROM ONE SEX TO THE OTHER. Secondary sexual characters, such as have been referred to in the last sec- tion, seem indissolubly associated with their corresponding sex. ‘The reason for such an association is obscure, but it is known that it is not due to the absence in the protoplasm of the characteristics of the opposite sex, for these may develop in the individual when the germ glands are removed. The germ glands, then, control the latency of the one set of characters and the patency of the other set. In poultry the removal of the sex glands from a young cock, in the process of caponizing, results in loss of the crowing instinct and failure of comb, wattles, spurs, hackle, saddle, and sickles to acquire the size characteristic of a cock. If in the fowl the germ glands fail to develop, the secondary sex characters are ambiguous. Despite this apparently physiological dependence of secondary characters in the germ gland, it seems improbable that the association is a necessary one. Almost all characters can be dissociated ; why not also sex and second- ary characters? There is reason to think much can be done in this way, because something has already been accomplished. For example, the cereb- 96 INHERITANCE IN POULTRY. ral hernia which now is found equally in both sexes of the Polish fowl was formerly a female secondary sexual characteristic. Bechstein (1793) states that he never observed the cranial dome in male Polish fowl. Blumenbach (1813), who made numerous dissections of the cranium of this fowl, states ‘‘of this deformity very slight traces indeed are found in the cocks, and these but seldom.’’* Consequently it must be concluded that the female secondary characteristic of cerebral hernia has been gradually transferred to the male sex also. A case of which the history is known even more defi- nitely is that of the Sebright Bantam. ‘This bird is characterized by the fact that in the male the hackle, saddle, and sickle feathers are of the same form as in the female; consequently the tail is short and truncate as in a hen. Here, apparently, female characteristics have become attatched to a male. Fortunately we have the history of the race from the mouth of the son of the maker, Sir Thomas Sebright. Dr. Horner, who obtained the state- ment from Sebright, published it in Tegetmeier’s Poultry Book (1868, pp. 241, 242). It was about the year 1800 that the late Sir John Sebright began to fashion the Sebright Bantam. The first cross was between a common Bantamt and the Polish fowl.t The chickens resulting from this alliance were bred in-and-in until the required markings and size were secured. Sir John then accidentally found a hen-tailed Bantam cock in the country where he was traveling. This short-tailed bird he in-bred with his newly manufactured Bantams, thereby giving their progeny the present form of the square tail. The essential characteristic of the race was thus gained from a mutative modification of a polymorphic characteristic.§ In my own experiments I have hardly proceeded far enough to get results ; yet already evidence of transference of color characteristics from one sex to the other is appearing. Thus in the second hybrid generation of the Cochin X Tosa cross at least one bird (No. 659 @ ) has hackles of a plain buff color like those of the male Tosa fowl, and entirely unlike the hackles of the female Tosa fowl or the female of the dark variety of the Cochin. Again, the female hybrids between the Dark Brahma hen and White Leghorn cock have much red on the wing coverts. This is foreign to the Dark Brahma hen, and must, so far as I can see, have been derived from the red on the wings of the male Tosa fowl. Finally, two male hybrids between the Tosa fowl and Dark Brahma show the feminine shafting. Experiments in con- tinuance of this investigation are, naturally, in progress. * Translation quoted by Tegetmeier, 1867, p. 173. + Doubtless Game Bantam is here meant. { The Golden Spangled Polish are undoubtedly referred to, whence the spangling of the feather was obtained. The combination gave the small size and gold-spangled plumage. § As might be anticipated from the notoriously sterile quality of hen-feathered cocks, Sebright Bantams are inclined to be sterile, and one is advised not to try to breed from the best show stock, 7. ¢., cocks with the shortest tails (Wright, 1902, p. 598). GENERAL, TOPICS IN INHERITANCE. 97 SEX IN HYBRIDS. There is a widely held and frequently expressed opinion that hybrids show an excessive proportion of males. Bateson and Saunders (1902, p. 139) probably have this in mind in their statement—“‘ the statistical distribution of sex among first crosses shows great departure from the normal propor- tions.’’? I have therefore been interested to tabulate the sex proportions in my hybrids. Without giving the full table, I may state that the totals are: Males, 204; females, 173; sex undetermined, 573. There is here an excess of males; but in view of the large early death rate, this may well be due to a difference in the death rate of the two sexes. Taking the different series of hybrids separately, most of them gave an approximation to equality of the sexes. One of the most striking departures is the series of Dark Brahma (121 2) X Tosa (8A ¢) hybrids. Of 22 individuals that developed to 18 days in the incubator, all but one grew to maturity. Of these 21, 16 are males and 5 females. The first egg laid by the Dark Brahma after she was put with the Tosa fowl developed into a female; the next nine that hatched were males; also her last six young were males. The exceptions to the law of equality of sexes in hybrid offspring are thus individual and not of general significance. CORRELATION OF CHARACTERISTICS. Every taxonomic description testifies to the fact that a certain set of characteristics is usually found associated in each species or variety. The prevailing theory has been that this association is a necessary one, maintained because all the characters are necessary to the success of the species in its relations to external environment, or else that they were physiologically inter- dependent. Modern work in hybridizing is establishing the fact that few of the specific characteristics are interdependent. Their association is, so far as interaction goes, mostly accidental. Thus in my experiments with poultry I have merely reached the same conclusions as have been gained by Johannsen (1899, p. 185), de Vries (1903, p. 494), and indeed all recent workers. I find, namely, that of the scores of evident external characteristics of poultry that are inherited in alternative fashion scarcely two can be found that are always associated. The most striking exception is the association of high nostril and absence of single comb. What, then, is the meaning of correlation in nature? Clearly it is only rarely due to physiologieal interdependence. It may often be due to an unrelated association of characters independently advantageous to the organ- ism. It is doubtless due to an accidental association of characters brought into the race bysuccessive mutations or by hybridizations and never disturbed, because not prejudicial to the well-being of the species. 98 INHERITANCE IN POULTRY. THE MUTATION THEORY IN ITS RELATION TO THE ORIGIN OF DOMESTICATED ANIMALS. While the mutation theory of de Vries has received widespread adherence among botanists, many students of animals, and especially of domesticated races, have appeared asitsopponents. Foremost among these are Professors Keller, of Zurich (1905), and Plate (1g05), of Berlin. I think that the essence of the mutation theory is too little apprehended. It rests on the funda- mental theory of heritable unit characters and assumes their very limited mutability. It recognizes the important results wrought by artificial selec- tion, but considers them as arising from two processes—first, the selection of minute favorable variations of the fluctuating sort, and, secondly, the preser- vation of new unit characters suddenly appearing. Such unit characters can usually be not only maintained but much improved by subsequent selective breeding. Now, it is true that breeders nowadays do not regularly wait for favorable qualities to cropout. The process is too slow, uncertain, andexpensive. If one had scores of thousands of individuals, desired mutations would come more frequently ; but even then they would rarely be of a desirable sort. Every breeder can, on the other hand, improve any characteristic by selec- tion, and that is for the most part the only method of improving a quality that is open to him. Of course he can make new coméinations of qualities by crossing, but this does not, typically, result in new gwalities. The question of the permanence of the improvement wrought by seleetion of minute variations is the first point of difference between de Vries and Keller. De Vries asserts that such improvement persists only so long as selection is maintained. Keller adduces some interesting cases on the other side, and the cogency of some of his evidence must be admitted. He traces the gradual evolution in Egypt of long lop-eared hounds from straight-eared ones. Ear length in rabbits, as Castle (1905, pp. 125-126) has shown, is not a unit character ; at least, it blends in hybridization and consequently exhibits any desired intermediate condition. The same is probably due for dogs ; consequently this character may well have arisen by summation of minute variations. Yet Keller goes on to show the long-eared condition has per- sisted in central Africa, where selective breeding no longer occurs. Hence one characteristic originated by selection of fluctuations has not retrogressed on removal of selection. The preceding method of proof is not, however, of general validity. Evidence that a characteristic arisen in domestication does not disappear when the race becomes feral again is not evidence against the permanence of fluctuations unless it is also proven that the characteristic arose by selec- tion of fluctuations. This is usually not the case. The instance of long ears would seem to be peculiar. Some of the other examples offered by Keller of persistence of characteristics despite discontinuance of selection avail little, since the precise origin of the unit characters concerned is un- GENERAL TOPICS IN INHERITANCE. 99 known. If, tuconsciously or not, a unit character arising as a sport has been preserved under domestication, it will persist even though the race bearing it become feral. Positive support for the mutation theory is gained from a consideration of the characteristics of poultry. Our study has shown them to be, for the most part, of the order of integral unit characters. As such they could hardly have been ‘‘ gradually built up.’’ eing indivisible they must have appeared at once, roughly in their presentform. The very existence of unit characters is proof of the mutation theory. That many characteristics of organisms have not been built up, but have suddenly appeared complete, may be inferred from peculiarities of the char- acters other than their integral nature. Fr, first, not all kinds of charac- teristics have been evolved in domestic poultry, but for the most part only such as occur elsewhere among wild races. Thus, for example, booted feet, as found in the grouse; crest on head, as seen in the umbrella bird (Cephalop- lerus), and long tail, as seen also in the widow bird (Chera). Secondly, many of the characteristics of domestic poultry are of the order of mutations in so far as they are almost pathological, ¢. g., taillessness, rose comb, silky and frizzled feathers, cerebral hernia, polydactyl feet, albinism. These char- acters, cropping out in the sporting organism and not being prejudicial to its well-being, have been preserved by the fancier; they doubtless arose sud- denly, as we find arising suddenly to-day other characters, which we discard because incompatible witha healthy stock—such as featherlessness, cross-bill, and imperfect development of toes. If these characteristics appeared sud- denly and not by being ‘‘built up,’’ as we know is the case, then so, doubt- less, have others. ‘The evidence that many, if not most, characteristics of poultry have arisen suddenly, without having been sought and laboriously built up by man, is convincing, and there can hardly be any escape from the conclusion that here evolution has bee largely, though not exclusively, by mutation. stele) INHERITANCE IN POULTRY. E. SUMMARY OF CONCLUSIONS. (1) Poultry exhibit numerous unit characteristics which do not blend in hybridization, but are inherited in alternative fashion. The unit characters are not immutable things in hybrids, but subject to modification—perhaps permanent—by interaction of the alternative characters. (2) Although the great majority of characteristics of poultry are inherited alternatively, yet a few cases of color characters show a particulate inher- itance. The comparative rarity of blending of characters makes it easier to see how new characters will not be ‘‘swamped by intercrossing with the parent form’’ (page 82). (3) Specific and varietal characteristics in de Vries’s sense are not inherited in a markedly different fashion, although in two cases progressive variants do not Mendelize typically. (4) The patent characteristic is usually dominant over its latent allelo- morph. (5) Old and new characteristics are equally dominant. (6) Dominance and recessiveness of characteristics are not always accom- paniments of their segregation in the germ cells; both, moreover, are fre- quently incomplete. (7) Dominance is usually, but not always, independent of the races crossed. (8) Prepotency is as truly important in inheritance as dominance. (9) Many first hybrids exhibit special forms, due to the interaction of the two allelomorphs. ‘These may become fixed as new characteristics. (10) Reversion is being explained by the persistence in a ‘‘latent’’ condition of the latent character. (11) An adequate theory of gametic purity has not only to explain the simple Mendelian formula, but also the facts of imperfect dominance, im- purity of extracted forms, latency and atavism, and occasional particulate inheritance. (12) Reciprocal crosses exhibit differences due to the fact that the father and the mother transmit different kinds of characteristics. (13) When the parent races are dimorphic each sex in the hybrids exhibits the respective sex characteristic of both of the species. In many cases a new form of sexual dimorphism appears in the hybrids. (14) Certain characteristics of one sex may become transferred to the other by hybridization, owing to lack of complete correlation between primary and secondary sex characters. (15) The proportion of the two sexes in hybrids is normal. (16) With few exceptions, correlated characteristics easily separate as a result of hybridization so that any conceivable combination may be effected. CARNEGIE INSTITUTION, STATION FOR EXPERIMENTAL EVOLUTION, CoLp SPRING Harsor, February 72, 7906. LITERATURE CITED. IOL F. LITERATURE CITED. AMERICAN POULTRY ASSOCIATION. 1905. The American standard of perfection. Illustrated. A complete description of all recognized varieties of fowls. Published by Amer. Poultry Assoc. 1905. 299 pp. BALDAMUS, A. C. E. 1896. Illustrirtes Handbuch der Federviehzucht. Erster Band: Die Hiihnervogel. 3 Aufl. bearbeitet ven O. Griinhaldt. Dresden: Schonfeld. 1896. xvi + 476 pp., 102 figs. BATESON, W., and SAUNDERS, Miss E. R. 1902. Report I to the Evolution Committee of the Royal Society. London: Harri- son. 160 pp. : BaTESON, W., and PUNNETT. 1905. Experimental studies in the physiology of heredity—Poultry. Report II to the Evolution Committee of the Royal Society. pp. 99-131. BECHSTEIN, J. M. 1793. Gemeinniitz. Naturgesch. Deutschlands. Bd. 3. Sumpf-u. Hausvogel. Leip- zig: Vogel [teste Darwin, 1876]. BLUMENBACH, J. F. a 1805. Handbuch dervergleichenden Anatomie. Gottingen : Dietrich [teste Darwin, 1876]. 1813. De anomalis et vitiosis quibusdam nisis formativi aberrationibus Cum tab. 4°. Gottingen : Dietrich. . BORELLI, P. : ? : F 1670. Historiarum et Observationum medicophysicarum Centurize Iv. Francofurti. BoveERI, T. 1902. Ueber mehrpolige Mitosen als Mittel zur Analyse des Zellkerns. Verh. d. phys.- med. Ges. zu Wiirzburg. N. F. Bd. xxxv. CANNON, W. A. 1902. A cytological basis for the Mendelian laws. ull. Torrey Bot. Club. Vol. 29. Caste, W. E., and ALLEN, G. M. 1903. The heredity of albinism. Proc. Amer. Acad. of Arts and Sciences. XXXvII, 603-622. April. CasTLE, W. E. 1903°. The heredity of ‘‘Angora’’ coat in mammals. Science, n. s., XVIII, 760, 761. Dec. II. 1905. Heredity of coat characters in guinea-pigs and rabbits. Publication No. 23, Carnegie Institution of Washington. Papers of Station for Experimental Evolution No. 2. 78 pp., 6 plates. Feb. CHAMBERLAIN, B. H. 1900. Note on a long-tailed breed of fowls in Tosa. Trans. Asiatic Soc. Japan, XXVII. CLAYTON, J. 1693. Philosophical Transactions of the Royal Society of London, 1693, p. 992. CoRRENS, C. 1900. Mendel’s Regel tiber der Verhalten der Nachkommenschaft der Rassenbas- tarde. Ber. d. deut. bot. Ges , xvitr, 158-168. Sitzung von 27 Apr. 1905*. Gregor Mendel’s Briefe an Carl Nageli, 1866-1873. Ein Nachtrag zu den verOffentlichten Bastardierungsversuchen Mendels. Abh. math.-phys. K1]. k. sachs. Ges. d. Wiss., XXIX, No. 3, pp. 189-265. 1905”. Einige Bastardierungsversuche mit anomalen Sippen und ihre allgemeinen Ergebnisse. Jahrb. fiir wiss., Bot. xri, Hft. 3, pp. 458-484. Taf. v [April]. 1gos°. Zur Kenntnis der scheinbar neuen Merkmale der Bastarde. Bericht der _. Deutschen Botan. Gesell., xx11r, 70-85. 19054. Uber Vererbungsgesetze. Berlin: Borntraeger. 43 pp., 4 figs. 102 INHERITANCE IN POULTRY. CuENoT, L. ; 1903. L/hérédité de la pigmentation chez les souris (2™° note). Arch. de zool. expér. et gén. (4) 1. Notes et rey., pp. xxxiii-xli. CUNNINGHAM, J. F. 1903. Observations and experiments on Japanese long-tailed fowls. Proc. Zool. Sec. London, 1903, I, pp. 227-250. Darwin, C. 1876. The variation of animals and plants under domestication. Second edition, revised. Vols. 1,11. New York: D. Appleton & Co. [References made, in brackets, to pages of reprint by D. Appleton ‘' Fcurth thousand, 1894.’’] DAVENPORT, C. B. , ; 1g04. Wonder horses and Mendelism. Science, XIX, 151-152. Jan. 22. DE VRIES, H. 1889. Intracellulare Pangenesis. Jena: Fischer. 212 pp. 1900. Sur la loi de disjonction des hybrides. Compt. Rend. de l’Acad. des Sci. Paris. 26 mars. 1902. Die Mutationstheorie. WVersuche und Beobachtungen iiber die Entstehung der Arten im Pflanzenreich, Zweiter Band. 1. Lieferung, pp. 1-240. 1903. Die Mutationstheorie. 1. Bd. 2. Lief, pp. 241-496. 1905. Species and varieties: Their origin by mutation. Ed. by D. T. MacDougal. Chicago : Open Court Publishing Co. 1905. xviii-+ 847 pp. DURIGEN, B. 1886. Die Geflugelzucht nach ihrem jetzigen rationellen Standpunkt. Berlin: Parey. 880 pp. 80 Taf u. 101 fig. in text. FockE, W. O. 1881. Die Pflanzen-Mischlinge. Ein Beitrag zur Biologie der Gewachse. Berlin: Borntraeger. iv + 567. GaLTON, F. 1883. Inquiries into human faculty. London: Macmillan. 1889. Natural inheritance. New York and London. ix + 259 pp. HAACKE, W. 1893. Gestaltung und Vererbung. Eine Entwickelungsmechanik der Organismen. Leipzig: T. O. Weigel Nachfolger (Tauchnitz). vi-+ 337. HACKER, V. 1904. Bastardirung und Geschlechtszellenbildung. Zoe]. Jahrb., Suppl. vi (Fest- schrift fur Weismann). HAGENBACH, E. 1839. Untersuchungen tiber den Hirn-und Schadelbau der sogenannten Hollen- hihner. Archiv. fur Anat. Physiol. u. wiss. Med. (Muller) Jg. 1830, pp. 311-331, Taf. Xvi. Horst, C. C. 1904. Mendel’s discoveries in heredity. Trans. Leicester Literary and Philos. Soc., VIII, pp. 121-134. June. 1905. Experiments with poultry. In Report II to the Evolution Committee of the Royal Society (by Bateson ef a/.). London: Harrison. 154 pp. JOHANNSEN, W. 1899. Sur la variabilité de l’orge considerée au point de vue spécial de la relation du poids des grains a leur teneur en mati€res azotiques. C. R. trav. de Lab. de Carlsberg. Iv. Heft., 4, pp. 122-192. KELLER, C. 1905. Die Mutationstheorie von de Vries im Lichte der Haustier-Geschichte. Arch. fiir Rassen-und Gesellschafts-Biologie. 11 Jg., 1. Heft., pp. 1-19. Feb. LANGKAVEL, B. 1886. Hiihner mit sechs Zehen. Der Zoclogische Garten., XXVIII, p. 35. Jan. Lucas, P. 1847. Traité philosophique et phvsiologique de l’hérédité naturelle dans états de santé et de maledie du systéme nerveux., etc. Tom.1I. Paris: J. B. Bail- liére. 1847. 24-4 626 pp. 1850. [Same title.] Tom.11. Paris: J. B. Bailliére. 1850. 936 pp. LITERATURE CITED. 103 McCiune, C. E. 1905. The chromosome complex of orthopteran spermatocytes. Biol. Bull., vol. rx, No. 5, Oct., pp. 304-340. McGrew, T. F. rgor, American breeds of fowls. I. The Plymouth Rock. Bull. No. 29, Bureau of Animal Industry, U. S. Dept. Agr. Washington : Government Printing Office. 1go1*. American breeds of fowls. II. The Wyandotte. Bull. No. 31, Bureau of Animal Industry, U. S. Dept. Agr. Washington : Government Printing Office. 30 pp. 1904. The Shanghai or Cochin fowl. In Weir-Johnson-Brown Poultry Book. pp. 523-558. MENDEL, G. 1866. Versuche iiber Pflanzen-Hybriden. Verhandlungen des naturforschen Vereines in Brinn. Bd. Iv, 47 pp. More6avn, T. H. 1905. The assumed purity of the germ cells in Mendelian results. Science, vol. XXII, Ps No. 574, pp. 877-879. Dec. 29. NAGELT, C. v. 1884. Mechanisch-physiologische Theorie der Abstammungslehre. 1898. A mechanico-physiological theory of organic evolution, Summary. Transla- tion by F. A. Waugh. Chicago: Open Court Publishing Co. 53 pp. PETERSEN, C. E. 1905. The Houdan. In Weir-Johnson-Brown Poultry Book, 1904-05 (9. v-). PLATE, L. 1905. Die Mutationstheorie im Lichte zoologischer Tatsachen. C. R. du 6™° Congrés intern. de Zool. Berne. 1904. 203-212. May 25. ROMANES, G. J. 1got, Darwin and after Darwin. I. The Darwinian theory (third edition). Chicago: Open Court Publishing Co. STANDFuss, M. 1896. Handbuch der palaarktischen Gross-Schmetterlinge fiir Forscher und Sammler. Jena: Fischer. xii-+ 392. 8 Taf. Sutton, W. S. 1902, On the morphology of the chromosome group in Brachystola magna. Biol. Bull., rv, No. 1, pp. 24-39. Dec. 1903. The chromosomes in heredity. Biol. Bull., vol 1v, No. 5, pp. 231-251. April. TEGETMEIER, W. B. 1856. On the remarkable peculiarities existing in the skulls of the feather-crested variety of the domestic fowl, now known as the Polish. Proc. Zool. Soc. Lond., 1856, pp. 366-368. Figures. 1867. The poultry book, etc. London: Routledge. viii + 356 pp., 30 colored plates, 36 uncolored figures. THORNDIKE, E. L. 1905. Measurements of twins. Archives of philosophy, psychology, and scientific methods. No.1, Sept. 64 pp. TSCHERMAK, E. 1904. Weitere Kreuzungsstudien an Erbsen, Levkojen und Bohnen. Zeitschr. ftir das landwirths. Versuchswesen in Oesterr. 1904. 106 pp. WEIR, H. ; JoHNnson, W. G., and Brown, G. O. 1g04-05. The poultry book. 3 vols. New York: Doubleday, Page & Co. xxii + I3II pp. WEISMANN, A. 1904. The evolution theory. Trans. by J. A. Thomson and M. R. Thomson. 2 vols. London: Arnold. xvi -+ 416 + 405 pp. Woops, F. A. f 1902-03. Mental and moral heredity in royalty. Popular Science Monthly. Aug. 1902—April, 1903. WRIGHT, L. 1g02. The new book of poultry. London, ete. : Cassell & Co. viii + 600 pp. WYckKOFF, E. G. 1904. The Leghorns. In Weir-Johnson-Brown Poultry Book. 1904-05 (q. v.)- ZIEGLER, H. E. 1905. Die Vererbungslehre in der Biologie. Jena: Fischer. 74 pp. 2 Taf. 104 INHERITANCE IN POULTRY. EXPLANATION OF PLATES. PLATE I. Fic. 1.—White Crested Black Polish, 25. One of the females crossed with the Single- combed Black Minorca (cf. fig. 3) to produce the female hybrid shown in ree Gh ((8I4 J 805) Fic. 2.—White Crested Black Polish, 430. To show the male type of the Polish race, which, when crossed with the Minorca (fig. 4), produces male hybrids like fig. 6. (H. A. H.) Fic. 3.—Single Comb Black Minorca, 2 13. The mother of the hybrids, Minorca X Polish, represented by fig. 5. Fic. 4.—Single Comb Black Minorca, f{ 12. The father of various Polish X Minorca crosses, of which a male is represented in fig. 6. Fic. 5.—First Hybrid between Polish and Minorca, pullet. Compare the females of the parental races, figs. I and 3. Fic. 6.—First Hybrid between Polish and Minorca, cockerel. Compare the males of the parental races, figs. 2 and 4. The figures marked H. A. H. are from photographs made by Mr. H. A. Hackett. PLATE I. 106 INHERITANCE IN POULTRY. PLATE II. Fic. 7.—The head of a Polish fowl, ¢ 3, with skin on left half of head dissected away. Shows cerebral hernia, and the relation to it of the thick skin and crest feathers lying above. Note also the culminal fold, high nostril, and rudi- mentary comb. The latter lies at the base of the comb and shows asa mottled area against the deep black of the anterior crest feathers. (H. A. H.) Fic. 8.—Head of a hybrid, ¢ 50, between Minorca ¢ 13 (fig. 3) and Polish ‘3 (fig. 7). Shows the Y-shaped comb lying in front of the crest. The comb is double behind, single in front. Fic. 9.—Head of a Minorca * Polish hybrid of the second generation. Theson of sucha pair as are represented in figs. 5 and 6. Note the reappearance of a large crest, high nostril, and rudimentary comb. (H. A. H.) Fic. 10.—Side of cranium of Polish fowl. Shows bony dome covering cerebral hernia. yh 108 INHERITANCE IN POULTRY. PEATE Ene Fic. 11.—Head of hybrid of the second generation, Minorca < Polish, 371 {—the son of such a pair as are represented in figs. 5 and 6. Note the absence (imper- fect) of crest, the high nostril, and the rudimentary comb. (H. A. H.) Fic. 12.—Head of Houdan (9). Shows crest, high nostril, and rudimentary comb. FIG. 13.—Foot of Houdan (f'9). Shows the two toes (in place of one) situated imme- diately below the spur. Fic. 14.—Head of second generation White Leghorn » Houdan hybrid, its father being like fig. 17. Shows the occurrence of both cerebral hernia and single comb on the same individual. (H. A. H.) I1o INHERITANCE IN POULTRY. PLATE IV. Fic. 15.—Single Comb White Leghorn (174). Note high single comb, plain head, clean feet with four toes, and white plumage. (H. A. H.) Fic. 16.—Houdan (2 8). Note crest, high nostril, rudimentary comb, mottled plumage, and muff and beard. Fic. 17.—First hybrid (f 87) between White Leghorn and Houdan. Note crest, Y comb, white plumage, muff, and double toe behind on left foot. PLATE IV. II2 INHERITANCE IN POULTRY. PLATE V. Fic. 18.—Dark Brahma hen (121), Note uniformity of plumage coloration, except that hackles are /aced with whit, and wing coverts, back, and breast are penciled. Comb of pea type. Feet booted. Vulture hock. (H. A. H.) FIG, 19.—Dark Brahma cock (122). Note laced hackles and saddles, prominent white wing bow, pea comb, and booted feet. I1t4 INHERITANCE IN POULTRY. PLATE VI. Fic. 20,—First generation hybrid, § 607, between Black Minorca (fig. 6) and Dark Brahma (fig. 19). Note prevailingly black plumage, with trace of white wing bow, irregular pea comb, slightly booted feet, and absence of vulture hock and of lacing on hackles. (H. A. H.) FIG. 21.—First generation hybrid, §\ 603, between Black Minorca and Dark Brahma. Brother to fig. 20. Note almost complete absence of white wing bow, but presence of white lacing on hackles. Note also high, though pea, comb, and long tail. Form of trunk like Dark Brahma, neck like Minorca. (H. A. H.) PLATE VI. Mh a eae 7 mM r16 INHERITANCE IN POULTRY. PLATE VII. FIG. 22.—First generation hybrid, 2 387, between White Leghorn Bantam (resembling fig. 15) and Dark Brahma (fig. 18). Note the new type of plumage colora- tion. Hackles broadly laced asin male, rest of plumage mottled, with much red. Booting rudimentary. (H. A. H.) FIG. 23.—First generation hybrid, 9 395, between White Leghorn and Dark Brahma. Shows reappearance of the Dark Brahma 9 type of coloration. (H. A. H.) PLATE VII. 118 INHERITANCE IN POULTRY. PLATE VIII. Fic. 24.—First generation hybrid, ¢\270, between White Leghorn and Dark Brahma. Shows the pure white type, 7. ¢., dominance of White Leghorn coloration. Note slight booting, absence of vulture hock and the erect, Leghorn tail. (H. A. H.) Fic. 25.—First generation hybrid, ¢‘ 409A, between White Leghorn and Dark Brahma. Shows the type with red on the wing coverts. (H. A. H.) 120 INHERITANCE IN POULTRY. PLATE IX. Frc. 26.—Black Cochin Bantam, 2 129. Shows short tail and heavily booted feet. The mother of the barred bird, fig. 27. (H. A. H.) Fic. 27.—First hybrid, §' 365, between Black Cochin Bantam (fig. 26) and White Leghorn (of. fig. 15). Note barred plumage coloration, red earlobe, and booted fect. (H. A. H.) Fic. 28.—Buff Cochin Bantam, $545. Note short tail, heavily booted feet, red earlobe, and single comb, 122 INHERITANCE IN POULTRY. PLATE X. Fic. 29.—Tosa fowl, 1A, imported from Japan. Long tail feathers had been recently pulled out. F1G. 30.—Tosa fowl, 2 2A, imported from Japan. Note the light shafting. F1G. 31.—Tosa fowl, 3A, ‘“‘Admiral Togo,’’ son of iA and 2A. Photographed Septem- ber 7, 1905. Note length of tail. (H. A. H.) Fic. 32.—White Cochin Bantam, 9 35a. This bird was crossed with fig. 29 and gave hybrids represented on plate XI. PLATE X. Free, (RUA) es 4 124 FIG. FIG FIG FIG INHERITANCE IN POULTRY. PLATE XI. . 33. First generation hybrid, 2 58, between White Cochin (fig. 32) and Tosa fowl (fig. 29). Note a slight broadening of shaft stripe as compared with female Tosa fowl. . 34.—First hybrid, § 53, between White Cochin and Tosa fowl (fig. 29). barring on feathers, and long tail. (H. A. H.) Note white . 35.—First hybrid, §' 95, between White Cochin and Tosa fowl, younger brother to fig. 34. Note barring and growth of saddle and tail feathers. (H. A. H.) . 36.—Second generation hybrid, ? 312, between White Cochin and Tosa fowl. Note pure white plumage color, like Cochin grandmother, fig. 32, combined with long tail of Tosa, fig. 30. (H. A. H.) PLATE Xl. 126 INHERITANCE IN POULTRY. PLATE XII. Fic. 37.—Plumage chart of F, (White Cochin Tosa), 2 58, at about 5 months. pl, to of head ; 2, hackle; 3, middle of back; 4, throat; 5, breast; 6, middle tail ; 7, saddle ; 8, wing, secondary. FIG. 374a.—Plumage chart of F, (White Cochin * Tosa), 153, atabout5 months. Signifi- cation of figures same as in fig. 37. Shows davring of feathers. Frc. 38.—Second hybrid generation (White Cochin * Tosa), 1315. Note reappearance of pure white like Cochin grandmother (fig. 32, plate X) ; form intermediate, feet booted. (H. A. H.) PLATE XI. 128 INHERITANCE IN POULTRY. PLATE XIII. Fic. 39.—Jungle fowl, © 2. Taken after death to show shafting on breast, nape, back, and wing coverts. FIG, 40.—First generation hybrid, ¢{ 358, between Dark Brahma (fig. 19, plate V) and Tosa fowl (fig. 29). Note white laced hackles and saddles, vulture hock, boot, and pea comb of Brahma and white earlobe and elongated head of Tosa. (HS A\ He) is ea a , a Sto, zi 130 INHERITANCE IN POULTRY. PLATE XIV. FIG. 41.—Frizzle fowl, f'15. Note rose comb and feathers that turn forward, forming a ruff on the neck. On the exposed vanes of the upper secondaries the twist- ing of the barbs may be seen. FIG. 42.—Frizzle fowl, 2 184. Note extreme curling of feathers, the absence of barbs on part of the secondaries, leaving the shaft quite naked, and the absence of plumage on the back of the head. Fic. 43.—Silky fowl, g/ 21a. Note single comb, small crest, the downy condition of the contour feathers, and the elongated aud disconnected barbs of the wing secondaries and tail feathers. Fic. 44.—First hybrid between Frizzle and Silky, § 219. Note the white plumage, rose comb, trace of crest, frizzled feathers (ruff !), and absence of elongated barbs on the wing, secondaries, or other evidence of silkiness. The booted feet and extra toe are derived from the Silky. (H. A. H.) 132 INHERITANCE IN POULTRY. PLATE XV. FIG. 45.—Rumpless Game, 2 49. Fic. 46.—Rumpless Game, (117. The hackles and saddles and wing bars are red ; other- wise the plumage is largely black. (H. A. H.) Fic. 47.—First hybrid between White Leghorn (cf fig. 15, plate [V) and Rumpless Game, 3\ 516. Note dominance of white (except for a trace of red on the wing coverts) and long tail. The comb is intermediate between that of a Game and that of a White Leghorn. (H. A. H.) PLATE XV, 134 INHERITANCE IN POULTRY. PLATE XVI. Fic. 48.—Head of second generation Minorca * Polish hybrid, ¢' 474. Shows last term of series, beginning with fig. 50 and passing through fig. 49, of reduction of median component of Y comb, leaving only two papilla remaining. (H. A. H.) Fic. 49.—Head of second generation Minorca * Polish hybrid. Shows middle term of series passing from Y comb to V comb, The niedian portion of the comb is represented by a carunculated mass at the base of the papillae. (H. A. H.) FIG. 50.— Head of second generation Minorca * Polish hybrid, §'259. Shows beginning degeneration of median component of Y comb, which ends in the V comb (fig. 48). (H. A. H.) FIG. 51.—Head of second generation Minorca * Polish hybrid. Shows 2 pairs of papille, high nostrils and rudimentary crest, indicating that the first two character- istics are independant of the third. H. A. H.) Fic. 52-—Dorsal view of head of (Minorca * Polish) * Minorca hybrid. Shows Y comb in which the median component extends between the arms of the Y, the whole resembling a peacomb. (H. A. H.) XVIs PLATE 136 INHERITANCE IN POULTRY. PLATE XVII. FIG. 53.—First generation hybrid between Silky and Jungle fowl, 9156. Shows domi- nance of Jungle-fowl plumage color and the extra toe and crest of the Silky. (HVAC EL FIG. 54.—First generation hybrid between White Leghorn and Rose Con b Black Mi- norca, 138. One of the two birds that exhibit the blue, Andalusian type of coloration, all others being white. (H. A. H.) XVII. PLATE a Sa NOILNLILS NOILALIL! “ Z NVINOSHLINS S3IYVYSIT LIBRARI NOILALILS LIBRARI LIBRARIES _ SMITHSONIAN YWY iT INSTITUTION NOILNLILSNI NVINOSHLINS SSIYVUds INSTITUTION INSTITUTION INSTITUTION ITUTION SMITHSONIAN Rw yVYai NOILNLILSNI NVINOSHLINS S3ZIYVYUEIT_LIBRARIES NVINOSHLINS S3I1YVUEIT LIBRARI! NVINOSHLINS S31YVudIT SMITHSONIAN SMITHSONIAN SMITHSONIAN LIBRARIES SMITHSONIAN. INSTITUTION NOILQLILSNI NVINOSHLINS S31uVvud! NOILNLILSNI NOILNLILSNI LIBRARIES WY LD LIBRARIES ITUTION NOILALILSNI_NVINOSHLINS S3!1YVYd!IT LIBRARIES SMITHSONIAN _INSTITUTIC 2 > INSTITUTION NOILNLILSNI ITUTION NOILNLILSNI NVINOSHLINS SSIYVUdIT LIBRARIES SMITHSONIAN _INSTITUTIO n re ee < [ee a aj z= S 5 ix Ll z ca i 5 = o = wo E Es) = 0 2 Ke > e > > = = - = = o m 2 m m = n = (2) a) LIBRARIES SMITHSONIAN INSTITUTION NOILNLILSNI NVINOSHLINS S3I1uVvuyd! Zs n Zee w Zz 22) "5 = = = = Y, = = z a z \ = iL py, = a ro) ae : (ily, O : ae 2 Ns AA? g = 2 E WN Zz. Ff ONS 2 Be dr dees 2 = ITUTION NOILNLILSNI_NVINOSHLINS S31YVYGIT LIBRARIES INSTITUTIO ue a a a = a = = aw = cc eat o = joe = joa = a ro) = re) a rs aj Fe si Zz pa z Yuvudit LIBRARIES INSTITUTION NOILNLILSNI NVINOSHLIWS SS3IYVYd! = 5 = 5 — «. 6 = = = E SNR OE =), 5 2 W€ =) > ey > - > & 2 e 2 = 2 c = 22) 2) Fees 2) a z o zZ o Zz n = = xe ‘S = 1], = < Sas 0 NS % n SHH lid Shy Ll 5 = 77) LIBRARIES SMITHSONIAN INSTITUTION NOILOLILSNI NVINOSHLIWS Saluvud EG NVINOSHLIWS WS SN N SMITHSONIAN @ ya NVINOSH NVINOSHLIWS SMITHSONIAN Yuva 2 rf Zz ws 2 aOR an ie = < hf a < F WGN CS c a Gy = « S NN fa rs) n "G 3 4 rs) 2 2 aay es -! z of TITUTION NOILNLILSNI NVINOSHLINS S3!1Y¥VYUdIT LIBRARI ES SMITHSON AN_INSTITUTIO NVINOSHLINS S31NYVYSIT LIBRARIES. SMITHSONIAN NOILALILSNI NVINC ars _— Ve = —) str " = * = = ms = = 5 i > = > so? ay ee = 2 = Eff, D bb : 5 2 Gy Z a Z a Z my Ze £ 2 = = z z 2 S 2 3 NVINOSHLIWS SMITHSONIAN SMITHSONIAN SMITHSONIAN G hi SMITHSONIAN SMITHSONIAN INSTITUTION NOILMLILSNI NVINOSHLIWS S3IYVUGIT LIBRARIES SMITH SMITHSONIAN INSTITUTION NOILNLILSNI NVINOSHLINS S31uvugia LIBRARIES SMITt 7) Ss o 3S 2 = is us = Ww 2 Awe Ww = w « “S Sj AS Fe gi Tee ES = _ SLO NY o — (ae WY <, = < a XS. re = < Vf oc par) o S o S o Gp ca : 5 = = a 5 B54 = ‘i oz = Zz eer z =A . NVINOSHLINS S3S!1YVYSIT LIBRARIES SMITHSONIAN INSTITUTION NOILNLILSNI_NVINC SNS Ss = z Zz eS a Se = eS a wo a o — Wy = be] N 2 e 2 S Gy, 5 2 : : : eae ; 2 NY oO = > ia Fee — X z Z HE Z Z 4 m) = = =e wn e) Zz > = NVINOSHLINS S3ltuvugia =a Z z Jy z z (7) eect Fa 7) ” : = _NVINOSHLINS S3IYVYSIT LIBRARIES SMITHSONIAN INSTITUTION NOILNLILSNI_ NVI a Ww a us Dee us a = = = = O° az = < = < = < i fz < a cc c ee = Ee c iS = e = sas te aa 5 ane 2 5 = 5 S = =u SMITHSONIAN INSTITUTION NOILNLILSNI NVINOSHLINS S3!YVUGIT_LIBRARIES SMITI a = z - z = = = + 2 eee Ce = S = gh pp ee) ke x AS = Be] = LY 2g ee NSO Oe = iY, = E a ‘ E a = i g Vio m n = D = BU =<, pony ” . = on _— " NVINOSHLINS S3IYNVYUGIT LIBRARIES SMITHSONIAN NOILMLILSNI NVINC z z See Sy te z Z z = = <2 RNS =) z Be es pa ae BS my 5S QGe® = x OL, re} gy 2X 2 SY ff 2 E 2 Er wn = 2 Uy = = > = eheaes > : = w a w” = a id w ; SMITHSONIAN INSTITUTION NOILONLILSNI NVINOSHLIWS S3INVUGIT LIBRARIES SMITI 1 LIBRARIES SMITHSO a S a Shh 3 Mp = Ra eee = B® NX g aay ae = eZ S PN 5 aff ae 5 Ee = = = GZ ee) Z, re} 2 iS) \ 5 San mak a5 - =< Py 7 ay _NVINOSHLINS _S3 (YVvug Ley ete LIBRARI ES_ SMITHSONIAN INSTITUTION _ NOILNLILSNI_NVING