576 EXPERIMENT STATION EECORD. 



" Tliere is no evideuce tbat the continued selection for higher egg production 

 practiced during the eight years covered by the experiment produced any in- 

 crease whatever in the mean egg production of any month in the year. On the 

 contrary, the mean production in all but two of the months actually decreased 

 during the period of selection. 



"The present data indicate that only a trifle more than a quarter of the total 

 eggs produced were laid in the winter third of the year (November 1 to March 

 1). In the first two-thirds of the laying year approximately three-fourths of 

 the total eggs are produced." 



These observed facts regarding the character of the distributions of variation 

 are accounted for by an hypothesis which includes the following ix)ints: 



" Variation or changes in the rate of fecundity in the hen are fundamentally 

 or innately continuous (in the mathematical sense), though the objective mani- 

 festation of fecundity is discontinuous, i. e., expressed in discrete units. 



" Visible egg production in each iudivdual bird tends to occur in definite cycles 

 or periods of varying length which alternate with nonproductive periods. 



" The rate of fecundity (amount of egg production per unit of time, conceived in 

 the sense of the differential calculus) is in any bird at a minimum at the begin- 

 ning of a cycle of production, increases to a maximum at what may be termed 

 the height of the cycle, and decreases to a minimum (usually quite rapidly) as 

 the end of the cycle is approached. 



" Each of the monthly fecundity distributions is compound, and made up of 

 two parts. In one part are included all birds which are well along in a period 

 of laying activity (or cycle of fecundity). The other part includes those birds 

 not laying at all (that is, in a nonproductive condition or period) and those that 

 have just emerged from this colidition of zero fecundity and started on a laying 

 cycle. 



"(1) The proportion of the whole flock which falls into each of these two 

 classes, and (2) the particular rate of fecundity which marks the boundary be- 

 tween the two classes, are not constant, but, on the contrary, change in a definite 

 and orderly manner in the different parts of the laying year. 



" The distribution of frequency wdthin each of the two hypothetical com- 

 ponents of the monthly fecundity distributions follows a simple, unimodal skew 

 frequency curve, and the curve describing the entire monthly fecundity distri- 

 bution is in each case the sum of two skew frequency curves." 



First Tasmanian egg-laying' competition, R. J. Terry {Agr. and Stock Dept. 

 Tasmania, Bui. 18, 1910, pi). 15, figs. 6). — In 28 competing pens of 6 birds each, 

 the average number of eggs laid per bird during the year was 161, and the 

 average cost of food per hen 6s. 9d. 



Cooperative marketing of eggs {Parmer, 29 {1911), No. 5, pp. 15'i-1oG, 

 figs. 3). — ^An account of the egg-selling associations in Minnesota and Ontario. 



Progress of poultry investigations {New England Homestead, 62 {1911), 

 No. 5, pp. 151, 161). — An account of the practical nature of the poultry work 

 and progress at some of the state experiment stations. 



Some results of castration in ducks, H. D. Goodale {Biol. Bui. Mar. Biol. 

 Lah. Woods Hole, 20 {1910), No. 1, pp. 35-66, pis. 5, figs. 6).— Castrated drakes 

 of the Rouen breed retained their secondary sex characteristics, except the 

 ability to assume summer plumage. The spayed ducks assumed, more or less 

 completely, the secondary sexual characters of the drake, but the change was 

 very gradual. It is suggested that the female owes her color to the presence 

 of some modifying element which prevents the development of the male color, 

 and that the modifier may sometimes be responsible for sex limited inheritance. 



A bibliography is appended. 



