106 MASS. EXPERIMENT STATION BULLETIN 211. 



Continued Use of Breeders on the Basis of the Performance of their Offspring. 

 Birds used as breeders are kept till the records of their progeny are at 

 hand. Many fail to transmit the desired qualities, either wholly or to a 

 sufficient number of their progeny, and therefore are discarded. Excep- 

 tions are sometimes made with females that are otherwise remarkable, in 

 the hope that they may nick better wdth another mate. Those birds 

 that show pronounced ability in producing offspring that make egg 

 records of the desired type may be bred several years in succession. The 

 importance of a very few birds of this sort cannot be too greatly empha- 

 sized, for through these progress is made. 



Points in Management that affect the Results. 



A few points in the handling of the flocks need especial emphasis, as 

 they bear directly on the interpretation of the results. 



Flock Number. — Throughout these experiments the pullets have been 

 kept in relatively large flocks, 100 to 125, while making their records, 

 with the following exceptions: in 1912-13 there were two pens of 72 

 birds each; in 1913-14 there was one pen of 72 birds and several smaller 

 groups of 25 to 35 each; in 1914-15 the pedigreed pullets were in large 

 flocks, but the new stock was in smaller groups. The latter are excluded 

 from the averages. Some years the high-line birds, or part of them, have 

 been penned by themselves; other years they have been scattered through 

 the flock. They have received exactly the same treatment that was given 

 the rest. 



The selection of the pullets that are put into the laying pens is based on 

 the family. The best families having been decided upon, all the daughters 

 in those families are included except those of exceedingly poor vitality, 

 amounting to less than 5 per cent. As far as possible, families (offspring 

 of one mother) containing fewer than seven daughters each are excluded. 

 This has been done in order to enable a fair judgment of the breeding 

 abUity of any mother to be made. An exception was made to this rule 

 in 1920-21, when all daughters weighing less than 3 pounds 6 ounces at 

 four months of age were excluded. The effect of such exclusion, if any, 

 on egg production is slight, as shown by correlation tables. 



The time of year in which a flock of birds is hatched is one of the most 

 important factors in determining the number of eggs laid. This is illus- 

 trated in several figures and tables, of which Fig. 13 (page 117) may be 

 especially cited. Note that the late hatched flock loses about two months' 

 production, — a production that, as far as the records show, is not com- 

 pensated for, except in slight measure, at other seasons. 



It is the practice at this station to hatch weekly. The length of the 

 hatching season has varied from year to year, but, unless otherwise stated, 

 only records made by birds hatched between March 25 and May 14, in- 

 clusive, are presented in this paper. The mean hatching date is April 18, 

 from which the several j'early means vary little as shown by Table II. 



