FERTILITY 97 



the case of swine this law is undoubtedly a true statement 

 of what actually happens. This law not only applies 

 to mammals but is also found in poultry. Geyelin 1 has 

 attempted to formulate an average of fertility in poultry 

 in relation to age in the following table : 



First Year after hatching . 

 Second Year after hatching 

 Third Year after hatching . 

 Fourth Year after hatching 

 Fifth Year after hatching . 

 Sixth Year after hatching . 

 Seventh Year after hatching 

 Eighth Year after hatching 

 Ninth Year after hatching . 



15 to 20 eggs 



100 to 120 eggs 



120 to 135 eggs 



100 to 115 eggs 



60 to 80 eggs 



50 to 60 eggs 



35 to 40 eggs 



15 to 20 eggs 



1 to 10 eggs 



These estimates must be regarded as far below the 

 performance of well-selected flocks maintained under 

 good conditions of food and shelter. The age at which 

 pullets begin laying varies greatly, depending upon their 

 development. At the Ohio Experiment Station, a White 

 Leghorn pullet began laying at four months and fifteen 

 days old. At the Missouri Experiment Station Kempster 2 

 reports a White Leghorn pullet beginning to lay at four 

 months and nineteen days of age. The number of eggs 

 laid by old hens may also greatly exceed the figures given 

 by Geyelin. At the Maine Experiment Station a hen 

 laid 111 eggs during her ninth year. 3 



A remarkable case of fecundity in sheep is noted by 

 Pearl. 4 A ewe owned by Barrett for nineteen years 

 gave birth to thirty-six lambs which were distributed 

 during the breeding life of the ewe as follows (page 98) : 



1 Geyelin, quoted by Marshall, loc. cit., p. 590. 



2 Unpublished records, Missouri Experiment Station. 



3 Maine Experiment Station, Bulletin 266. 



4 Pearl, Science, vol. 37, p. 227. 



