1918] ANIMAL PEODUCTION". 269 



which linkage is the same in both sets of gametes, and that in which linkage 

 is complete in one set. 



In each system general formulas are derived for transforming generation n 

 into generation n+l. In several systems special formulas are given for finding 

 directly in any later generation n the proportions of the population, when one 

 begins with parents that are a cross between ABAB and abab, or between 

 AbAb and aBaB. With regard to selection and assortative mating with respect 

 to a single character, formulas are given for the effect on the single pairs taken 

 separately ; thus, for the effect of selection or assortative mating with respect to 

 one character on the distribution of another character linked with that one. 

 The formulas are collected for convenience in 31 tables in the appendix. 



Some breeding- properties of the generalized Mendelian population, E. N. 

 Y/KNTWOKTH aud B. L. Remick {Genetics, 1 (1916), No. 6, pp. 608-616) .Some 

 properties of mating a generalized Mendelian population r AA+s Aa+t aa are 

 considered in this paper, random mating (two types of assortative mating aud 

 mating of dominants alone) being considered. Formulas are presented which 

 will give the expected proportions of AA, Aa, and aa in any generation result- 

 ing from the practice of such matings. 



Studies on inbreeding-. — VIII, A sing-Ie numerical measure of the total 

 amount of inbreeding, R. Pearl (Amer. Nat., 51 (1917), No. 610, pp. 636-639, 

 fig. 1). — The author describes a single numerical constant which has been de- 

 vised to supplement or replace the inbreeding curve (E. S. R., 38, p. 65) as a 

 designation of the total inbreeding exhibited in a particular individual. By the 

 method it is seen that American Jersey cattle, as judged by random samples 

 of the general population, are about 28 to 30 per cent as closely inbred as the 

 maximum possible amount, taking account of the first eight ancestral genera- 

 tions as a whole. 



Tricolor inheritance. — II, The Basset hound, H. L. Ibsen (Genetics, 1 (1916), 

 No. 4, pp. 367-376, figs. 2).— This part of this series (E. S. R., 35, p. 770) dis- 

 cusses the probable genetic factors involved in the production of the coat color 

 in Basset hounds, the relation of these factors to each other, and test matings 

 which could be made to determine how closely the factors and relationships 

 proposed fit the actual cases. 



Basset hounds are of two kinds, (1) tricolors, and (2) tan-and-whites. 

 Black-and-whites do not occur in the breed. Tricolors are described as " black, 

 white, and tan, the head, shoulders, and quarters a rich tan, and black 

 patches on the back." Tan-and-whites have tan heads and " tan is often found 

 on the back." 



The factors involved in color inheritance in Basset hounds are (1) B, the 

 factor for black, always present in Bassets; (2) E, the extension factor which 

 extends the black (or chocolate) and may be present or absent; (3) T, the 

 factor for uniform pigmentation (animals without T are either black-and-tan, 

 liver-and-tan, or red (tan) and lemon; T is always absent in Bassets) ; and 

 (4) R, the factor which inhibits the formation of black (or chocolate) pig- 

 ment in the coat (it is questionable whether this factor is ever present in 

 Bassets). Tricolors may be of the formula BBEEttrr or BBEettrr. Ee tri- 

 colors mated together get some ee offspring which are tan-and-whites and which 

 should breed true. These may have tan spots on the back. In this case, 

 when T is absent, the tan on the head should be of a lighter shade than the 

 tan on the back. If R is present in Bassets then BBEE (or Ee) ttRr tan-and- 

 whites (with tan on the back) bred together should get some tricolor off- 

 spring. This can not be determined from available data. 



Tricolor inheritance. — III, Tortoise-shell cats, H. L. Ibsen (Genetics, 1 

 (1916), No. 4, pp. 377-386) .—The author reviews the work of others and offers 

 44073"— 18 6 



