191S.] PUBLIC DOCUMENT — No. 31. 59a 



tives, and since his sisters almost always differ from each other 

 in several points, one is as likely as not to select a male cor- 

 responding to his poorest sister as to his best one. If, however, 

 numerous matings are made and tested, the chances of mating 

 good males to good females is increased in proportion to the 

 number of matings made. Thus the length of the job of pro- 

 ducing a strain averaging 250 eggs annually depends upon the 

 scale on which operations are conducted. 



We are sometimes asked why we do not keep our layers for 

 more than one year. The answer is that the pullets require all 

 the available space. Xow the annual renewal of the laying 

 flock is a large item on a commercial plant, and absolutely 

 necessary with available strains of American breeds. However, 

 there seems to be no biological barrier in the way of securing a 

 strain that will lay heavily year after year. 



The accumulation of data on hatching quality of eggs is being 

 continued as a part of routine procedure, but it has been 

 necessary to drop the attempt — as a separate piece of work — 

 to produce a strain whose eggs all hatch. 



The policy of rearing the chicks on clean ground, well isolated 

 from other fowl, has continued to yield splendid results. Al- 

 though no culling whatever was practiced during the growing 

 season, less than 2 per cent, of the pullets were unfit for the 

 laying houses. Moreover, such measures of isolation as it has 

 been possible to maintain have thus far secured freedom from 

 roup among the experimental pullets. 



It has been determined that crossing over takes place in the 

 sex chromosomes of the male fowl. 



Student Work. 

 Each year several seniors undertake a minor problem of in- 

 vestigation from which interesting preliminary results appear. 

 Thus Mr. Flint found that winter egg production in Rhode 

 Island Reds was independent of temperature. Mr. Graham 

 found that the length of a bird's laying period was the best 

 index of total production, although the time at which a bird 

 began laying (maturity) was also a good index. On the other 

 hand, rate of production during the spring months did not prove 

 to be a good index, contrary to the report of another station. 



