COUPLING 99 



of the data being upset by disturbing causes. He found 

 that hens fall into three grades : one laying over 30 

 eggs in their first winter, another under 30, and still 

 another none at all : and he found also that, in their 

 subsequent productivity, hens remain in the grades in 

 which they have begun. Dr. Pearl's dividing figure — 

 30 — ^must not, of course, be taken as an absolute fixture, 

 but as movable in some degree according to circum- 

 stances. 



When Dr. Pearl's discovery was known in this 

 country, Miss Murphy of the Munster Institute, Cork, 

 made the same observation but expressed it in a way 

 which is perhaps more effective in the mind of the 

 poultry-keeper. Miss Murphy found that spring-hatched 

 pullets are of three kinds : one beginning to laj"^ early 

 in winter — early in November even — and laying about 

 5 eggs a week till the end of January, another either 

 beginning equally early but laying only half as many 

 eggs or beginning near the end of winter and laying 

 at a slightly higher rate, and a third laying no winter 

 eggs at all or only a very few just at the end of winter. 

 The table on page 100 gives the numbers of eggs laid 

 during each week of the three winter months, November 

 and December 1913 and January 1914, by eight typical 

 hens belonging to each of these three classes. The 

 total eggs laid by each hen during the whole year from 

 November to November are also given. 



Thus Dr. Pearl's discovery is confirmed, and, judging 

 by the large amount of data at the Munster Institute, 

 we may take it that a hen laying over 30 winter eggs 

 will lay, in round munbers, from 150 to 220 before next 

 winter, one laying under 30 winter eggs will lay from 80 to 

 120, and one laying no winter eggs will lay from 40 to 60. 



