No. 1, July, 1920) GENETICS 113 



maximum of production is reached. After the time of maximum productivity, the absolute 

 production per uuii of time decreases with advancing age al a continually increasing rate. — 

 Menu fat percentage of the milk was found to decline with advancing age until the tenth year 

 of the cow's life is reached. Prom tin's point on, the fa1 percentage remain aboul constant 

 through tlic remainder of the milking Life of the cow. Weighted mean tandard deviations 

 and coefficients of variation for mean weekly milk yield was 2. sot; gallons and 17.081 per 

 cent, respectively. When all ages were Lumped together 3.329 gallons and 20.816 per cent. 



For fat percentage the weighted mean values for cows of any given age are: Mean =" ■'•'< 

 st andanl deviat ion ()..'i:i() and coellicient of variat ion = 8.827. — Relal ive variability of rnilk 



production is compared with other physiological characters; among others the udder as a 



Becrel ing organ is compared wit h t he oviduct of t he lien. It is shown t hat t he oviduct consid- 

 ered as a mechanism operates with somewhat less variability than does the udder, having 

 regard to the absolute weight of the product in the two cases. — Comparisons are made 

 tween the relative variability of mean weekly milk yield of these Avrshires and the daily 

 fluctuations in mixed milk of a large herd. (Such fluctuat inns are presumably due to environ- 

 ment alone since individual genotype is averaged.) The coefficients of variation stood in the 

 relation of 17.0S1 to 9.05 respectively. This is held to indicate that about one-half of the ob- 

 served variation in milk production results from the varying genotypic individuality of the 

 animals with respect to this character and that the other half results from varying environ- 

 mental influences. — The frequency curves were fitted by the use of Pearson type curves.— 

 Milk-production curves, analytically considered, tend definitely toward positive skewne 

 This is true in respect to yield and to quality. The weighted mean value of the skewness for 

 mean weekly yield is found to be + 0.1047, and that for fat percentage + 0.1338. These curves 

 for milk yield tend to fall more frequently in unlimited-range types, while those for fat per- 

 centage tend more to limited-range types. The estimation of range ends given by the theo- 

 retical curves are, on the whole, good. — In general the tendency of milk-yield curve is toward 

 the leptokurtic condition — that is, they are more peaked than the corresponding normal 

 curves would be. Fat percentage curves do not show any definite tendency with respect to 

 kurkosis. — Certain of the milk-yield curves were dissected into two normal curves by Pearson's 

 method. The resulting graduation was not so good as that given by the appropriate uni- 

 modal skew frequency curve. There is no evidence that variation curves for milk production 

 are bimodal. — John W. Gowen. 



698. Pearl, Raymond. Certain evolutionary aspects of human mortality rates. Amer. 

 Nat. 54: 5-44. 2 fig. Jan.-Feb., 1920. — Suggests that studies of vital statistics in man from 

 biological standpoint permit important evolutionary generalizations. Asserts that Inter- 

 national-Classification causes of death — 180 or more in 14 groups — is biologically unnatural. 

 Presents new classifications for purposes of particular investigation, somewhat changed from 

 International, based on particular group of organs breaking down and causing death, as 

 follows: (1) Circulatory system, blood and blood forming organs. (2) Respiratory system. 

 (3) Primary and secondary sex organs. (4) Kidneys and related excretory organs. (5) 

 Skeletal and muscular systems. (6) Alimentary tract and associated organs concerned in 

 metabolism. (7) Nervous system and sense organs. (8) Skin. (9) Endocrinal system. 

 (10) All other causes of death. — Gives tabular statistical data from U. S. of America, England, 

 Brazil (Sao Paulo), under each of ten grovips in descending-magnitude mortality from three 

 regions, per 100,000. Presents reasons for departure from International method in group 

 classification of many diseases. Tabulates relative importance (breakdown) of organ systems 

 in mortality with discussion. Groups rearranged in descending series on basis of data pre- 

 sented are as follows: (2), (6), (1), (7), (4), (3), (5), (8), (9).— Considers relative mortality 

 on basis of germ layers with interesting result that approximately 57 per cent are endodermal, 

 30-35 per cent mesodermal, 8-13 per cent ectodermal and assumes inverse correlation with 

 evolutionary degree of differentiation of the germ layers. Emphasizes importance of innate 

 factors as contrasted with environmental factors in influencing mortality. — L. B. Walton. 



699. Pearson, Karl. Inheritance of psychical characters. Biometrika 12:367-372. 

 1 pi. Nov., 1919. — The purpose of this article is to substantiate the claim of the inheritance 



BOTANICAL ABSTRACTS. VOL. IV. NO. 1 



