602 



THE AMERICAN NATURALIST [Vol. XLIX 



4. That selection on a progeny test basis was effective 

 is demonstrated not only by the general flock averages, 

 but also by the fact that it was possible to propagate sep- 

 arately high and low producing strains. The high pro- 

 ducing strains differed widely from the low producing in 

 mean winter production. Taking the average for seven 

 years in the case of the high, and four years in the case of 

 the low, it appears that the mean winter production of the 

 high producing strains was approximately two and a half 

 times that of the low producing strains. At the end of 

 the laying year 1911-12 the low producing lines were 

 dropped. In the next year (breeding season of 1913) no 

 birds were bred which were known to belong to segregat- 

 ing lines. Of course some were included which proved 

 afterwards to have been segregating, but this fact could 

 not, in any such case, have been told in advance from the 

 records in hand. The propagation of low producing 

 strains was attended with a great deal of practical diffi- 

 culty with the environmental conditions under which one 

 has to operate at this station. The growing season is 

 short. In order to grow properly a pullet for laying pur- 

 poses it is necessary that she be hatched after April 1 and 

 before June 1 at the latest, and preferably before May 15. 

 If, however, one selects birds which produce no eggs what- 

 ever before March 1, and use up some valuable time be- 

 fore they get well started in the spring cycle of laying it 

 becomes perfectly clear that one is automatically pre- 

 vented from getting any considerable number of early 

 hatched chicks from such mothers. If late hatched chicks 

 are used the results obtained as to winter production 

 later will not be critical. These circumstances make the 

 propagation of a low producing strain on a large scale 

 really a difficult proposition. There is of course no diffi- 

 culty in breeding birds which will not be winter layers. 

 One only needs to hatch in June, July or August. But 

 such birds will furnish no critical evidence regarding the 

 inheritance of winter production. 



5. The mean winter production for whole flocks over 

 the entire period of the investigation is 35.05 eggs. In 



