19161 ANIMAL PRODUCTION. 771 



In the experimental results it is shown " that tricolors may be of two kinds, 



those homozygous and those heterozygous for the c? or bhick-spotting fuctor; 

 that black-and-whites of tricolor parentage are also either homozygous or 

 heterozygous for the same factor; and that red-and-whites of tricolor par- 

 entage may carry the eP factor in a homozygous or heterozygous condition, 

 or it may be altogether absent, in which event the red-and-white breeds true. 



" Red-and-whites may be tested for the presence of the black-spotting factor 

 by mating them to homozygous self reds. If the factor is present there will 

 be tortoises among the offspring ; if it is absent they will be all self reds. 



" Black-and-whites of the tricolor series, homozygous for eP, produce only 

 tortoises when mated to homozygous self reds; if they are cPe half of the off- 

 spring are tortoises and the other half self reds. Both these kinds of black- 

 and-whites, therefore, produce some tortoises, but no self blacks when mated 

 to self reds. 



" Black-and-whites carrying E may be of three kinds, EE, EeP, and Ee. The 

 first kind when mated to homozygous self reds produce all self blacks; the 

 second kind, half self blacks and half tortoises ; the third kind, half self blacks 

 and half self reds. Black-and-whites carrying E, therefore, always produce 

 some self blacks when mated to self reds, but in some instances (when EeP) 

 also produce tortoises. 



" EE and Ee black-and-whites were produced by mating self blacks to ee 

 red-and-whites and inbreeding the Fi self blacks. Some of the F2 generation 

 are black-and-whites which are either EE or Ee. The first kind when mated to- 

 gether breed true. 



" Animals of the tricolor series carrying a large amount of black pigmenta- 

 tion (eP) and also a large amount of white spotting tend to produce a com- 

 paratively large number of black-and-whites and no eP red-and-whites. Those 

 carrying a small amount of black pigmentation tend to produce a compara- 

 tively large number of eP red-and-whites and no black-and-whites. 



" The statement is made, but complete experimental proof is reserved for a 

 later paper, that the three factors, E. complete extension of black pigment, eP, 

 partial extension, and e, nonextension, form an allelomorphic series." 



A bibliography of literature cited is given. 



Inbreeding in tail-female, W. H. E. Wankxyn (Bloodstock Breeders' Rev., 

 5 (1916), No. 2, pp. lJfO-lJi2). — The author states that inbreeding to the male 

 line has hundreds of prominent successes so far as to the female in her influ- 

 ence on future generations is concerned, while the results of inbreeding in 

 female-tail can be counted in small numbers. Examples of successes in female- 

 tail inbreeding are given. 



Sex control and known correlations in pigeons, O. Riddle (Amer. Nat., 

 50 (1916), No. 595, pp. 385-410, fig. 1). — The author states that the studies that 

 have thus far been made on sex and on the experimental control of sex in 

 pigeons go very far toward an adequate demonstration that germs prospectively 

 of one sex have been forced to produce an adult of the opposite sex — that germs 

 normally female-producing have, under experiment, been made to develop into 

 males, and that germs which were prospectively male-producing have been made 

 to form female adults. Neither selective fertilization, differential maturation, 

 nor a selective elimination of ova in the ovary can account for the observed 

 results. Further, and perhaps of more importance, these studies throw much 

 new light on the nature of the difference between the germs of the two sexes. 

 This difference seems to rest on modifiable metabolic levels of the germs ; males 

 arise from germs at the higher levels, females from the lower ; and such basic 

 sex differences are quantitative rather than qualitative in kind. 

 67476°— 17 6 



