558 



Journal of Agricultural Research 



Vol. XII, No. 9 



laying, in spite of marked differences in the value of the ratios from year 

 to year, are in agreement (with one partial exception) in having lower 

 ratios at each end of the season than in the middle. 



Table III. — Number of birds laying and number of pauses 



Number of birds laying 



Total number of 

 pauses 



Ratio of pauses to 

 number of birds lay- 

 ing (expressed in 

 percentage) 



Number without any 

 pause 



Percentage without 

 any pause 



Number with one or 

 more pauses 



Percentage with one or 

 more pauses 



34-7 



65. 22 



34-78 



104 

 51 



49.0 



57 

 54.81 



47 

 45- 19 



1915-16 



1916-17 



161 

 130 



81.0 



83 



SI- 55 



78 



48-45 



176 aSj 60 

 120 S3 



95 

 53-98 



100 86. 6 

 35 34 

 42. 17 56. 67 

 81 48 26 

 46.02.57.8345.33 



128 

 114 



89.0 



61 



47.66 



67 



52-34 



loi. 7; 100. c 

 88 



41. 9042. II 



104 121 



58. 10^57. 89 



145 

 13s 



89. I 93- I 

 61 



;o. 91 42. o 

 ic8 



266 

 300 



33-46 



177 



49-0957-9366.54 



303 



301 



99-3 

 133 



43-89 

 170 



56. II 



352 



267 



75-9 

 172 



376 



217 



57- 7 



213 



56-65 



163 



o A part of this flock was not trap-nested after March i. 

 SIGNIFICANCE OK THE PAUSES 



It appears from a consideration of the data presented in the preceding 

 paragraphs that pauses differ in their significance. It seems clear that 

 three classes at least can be distinguished : First, the long pause that is 

 clearly indicative of the presence of a winter cycle. The actual length 

 of this pause in exceptional instances need not exceed three or four days, 

 provided it comes at the proper season of the year, and is preceded by a 

 considerable period of egg production. Ordinarily, however, it exceeds 

 10 days in length. Second, short pauses which occur at frequent inter- 

 vals in the records of particular individuals because of their very 

 number must be regarded as having considerable significance (see Table 

 I, sire 6781). This type may be called "multipause" provisionally 

 and is to be distinguished from the type in which production is essen- 

 tially continuous, even though no sharp dividing line can be drawn 

 between these two groups. It is possible that certain records of the 

 multipause type represent a particular genotype, since there is a pro- 

 nounced tendency for many multipause records to occur in the same 

 families. This tendency has been particularly marked in a small flock 

 of Brown Leghorns. Another miultipause type results from intermittent 

 egg production during the winter pause. 



A third class includes those individuals which exhibit only one or two 

 short pauses. Some individual records probably represent extreme 

 variants of the multipause type, others pauses at the end of the winter 

 cycle, but the majority are clearly without particular significance. 



