758 EXPERIMENT STATION EECOED. 



pear premature to reject the former hypothesis for the latter until the posses- 

 sion of facts compels. 



A bibliography of the literature cited is appended. 



Studies on inbreeding. — VI, Some further considerations regarding cousin 

 and related kinds of mating, R. Pearl (Amer. Nat., 49 {1915), No. 585, pp. 

 570-575, fig. 1). — Cotitinning this series of studies (E. S. R., 32, p. 665), the 

 author gives coefficients of inbreeding for continued single and double cousin 

 mating and uncle and niece mating, with hypothetical pedigree tables illus- 

 trating these kinds of breeding. Illustrating graphically these coefficients of 

 inbreeding, together with those from the continued inbreeding of brother X sis- 

 ter and parent X offspring, it is seen that the curves fall into two pairs alike 

 for brother X sister and the double cousins, and for parent X offspring and 

 single cousin, except that the cousin curves lag one generation behind the others. 

 The uncle X niece curve is the same as the single cousin curve. From data pre- 

 sented in this and former papers, it is seen that inbreeding of any type when 

 continuously followed for about 10 generations results in within 1 or 2 per cent 

 of complete *' concentration of blood." 



The author extends the table of general equations given by Jennings (E. S. R., 

 32, p. 665) for coefficients of inbreeding after n generations of each particular 

 type of mating. 



An attempt to produce mutations through hybridization, F. N. Duncan 

 (Amer. Nat, 49 (1915), No. 585, pp. 575-582, fig. 1). — Crosses were made with 

 mutant stocks of Drosophila with wild stock from many localities in the United 

 States, from the West Indies, France, and Australia in order to discover, if 

 possible, whether hybridization is an essential factor in the formation of mutant 

 races. From 16,637 flies of the Fa generation, 7 flies arose which varied from 

 the normal type and bred true. Four of these soven cases arose from wild stock 

 just received from Illinois, so it is thought that the characters found to be in- 

 herited were recessive in the wild stock and not due solely to the cross. This 

 narrows the results to one mutant to every 5,545 flies, a ratio too wide to at- 

 tribute hybridization as its cause. 



In the light of these results, the author considers that mutations arise only 

 through chance. 



The nitrogenous metabolism products and their value in determining the 

 digestibility of the proteins of feed stuffs, A. Mokgen, C. Beger, and F. West- 

 HAUSSEB (Landw. Vers. Stat, 85 {1914), No. 1-2, pp. 1-104). — From their 

 studies with sheep and swine to determine the magnitude of the error oc- 

 casioned by the excretion into the alimentary tract and the voiding with the 

 undigested food of certain nitrogenous products of metabolism consisting of 

 the secretions of the gastroenteric canal (including the bile), together with 

 epithelial cells with some proteins and some other nitrogenous compounds of 

 a nonproteid nature, the authors conclude that a correction previously made, 

 which amounted to 0.4 gm. of nitrogen per 100 gm. of digested organic matter, 

 was not sufficient and that the figure should be increased to 0.85 gm. per 100 

 gm. of digested organic matter. 



Importance of calcium and phosphoric acid in the animal organism. — IH, 

 Value of the principal phosphorus compounds to the ruminant, G. Fingee- 

 xiNG {Landw. Vers. Stat, 86 {1915), No. 1-2, pp. 75-114) .—Results of experi- 

 ments in the feeding of casein, phytin, lecithin, nuclein, sodium nucleinate, and 

 disodium phosphate in rations to lambs indicated that an average of 89.2, 90.83, 

 92.72, 90.92, 93.62, and 90.53 per cent of the P2O5 in the respective phosphorus- 

 containing materials was retained by the animal body, while with goats the 

 percentages were 89.46, 96.81, 84.64, 88.54, 90.18, and 90.23. 



Previous work has been noted (E. S. R., 31, p. 71). 



