No. 1, February, 1921] GENETICS 29 



were high producers These experiments show that we are dealing with a situation 



that is complicated in many ways." III. Author points out necessity of control of all para- 

 sites in studying the inheritance of fecundity and describes "the quarantine method" of 

 rearing chicks. — W. A. Lippincott. 



196. GooDALE, H. D. Is the inheritance of egg production an insoluble problem? Jour. 

 Amer. Assoc. Instr. and Invest. Poultry Hush. 5:73, 74. 1919. — Author points out that 

 while improved egg production through selection is a demonstrated fact, the laws of the 

 inheritance of egg production have not been established. The latter present a complex prob- 

 lem because egg production is a complex character made up of several subsidiary characters, 

 the inheritance of each of which must be determined in advance. Five groups of difficulties 

 in the way of solving the problem of the inheritance of egg production are suggested in the 

 expressed hope that means of meeting them may be devised. These center around (1) the 

 purity of stock, it being unlikely that stock pure for any of the hereditary factors concerned 

 in egg production is in existence; (2) the need for larger numbers than may usually be secured 

 from a single pair; (3) the character is expressed in one sex only, making it necessary to judge 

 the genetic composition of males by their daughters; (4) the character is very sensitive to 

 environmental diflferences which are difficult to avoid; and (5) the presence of insidious but 

 unrecognized disease in the experimental flock, and the problems of disease resistance. — 

 W. A. Lippincott. 



197. GowEN, John W. Studies in milk secretion, V. On the variations and correlations 

 of milk secretion with age. Genetics 5: 111-188. 9 fig. Mar., 1920.— A thorough biometric 

 analysis of milk production in a single herd of Jersey cattle, involving 1741 eight-month 

 lactation records. The mean and standard deviation are given for each age, together with 

 the other constants necessarj' for fitting each distribution with the approximate skew curve. 

 It is pointed out that there is a sufficiently close approach to the normal curve to justify 

 use of the latter in many cases. Milk yield is found to rise to a maximum at 7.2 years, slowly 

 falling thereafter, the whole curve being fitted best by a logarithmic function. The varia- 

 bility at different ages rises and falls in a somewhat similar curve which is fitted with a cubic 

 parabola. The correlation between the yields at any two ages is found to average +0.54, 

 there being little difference between the value for successive lactations and lactations more 

 widely separated in time. The correlations between the yield in one lactation and the total in 

 various combinations of lactations were also found, that between the first and four following, 

 for example, being +0.65, and that between the first four and the fifth being +0.69. Regres- 

 sion formulae are given for calculating the most probable yield in a given year or group of 

 years on the basis of a single lactation. The use of these formulae in culling a herd is 

 discussed. — Sewall Wright. 



198. GowEN, John W. Studies in milk secretion. VI. On the variations and correla- 

 tions of butter-fat percentage with age in Jersey cattle. Genetics 5 : 249-324. 8 fi^. May, 

 1920. — The material for the study is taken from 1713 eight-months records of pure-bred 

 Jersey cows, made in one herd under uniform conditions and management. Correlation 

 coefficients and observed and theoretical means indicate the highest percentage butter-fat 

 with the first lactation period, and a slight decline in percentage butter-fat with each addi- 

 tional lactation period. The standard deviation and the coefficient of variation for the 

 butter-fat percentage for different ages — or succeeding lactation periods — remained approxi- 

 mately the same. The percentage fat for any one lactation period of a cow is an accurate 

 indication of the butter-fat percentage to be expected in future lactation periods. — The dif- 

 ference for the correlation coefficients for one lactation's butter-fat percentage with that of 

 another lactation, and for one lactation's butter-fat percentage with the butter-fat percent- 

 age over four lactation periods, gives a means of measuring the effect of environmental 

 changes on the butter-fat percentage. It was found that the internal mechanism of the 

 cow, which is probably hereditary, exercises six times the effect, in controlling butter-fat 

 percentages, that the environmental changes have. The factors that control the butter-fat 

 percentages have the same relative strength throughout the life of the cow to the exclusion 

 of any group of factors acting for short periods. — R. R. Graves. 



