THE BREEDING OF CHICKENS 107 



Cessation of Fertility. — In experiments with twenty Single 

 Comb White Leghorn hens, Waite^ found that fertihty 

 held up well for eleven days, and one egg was found to be 

 fertile after the male bird had been removed for twenty 

 days. Blttenbender^ reports a Barred Plymouth Rock hen 

 that produced a fertile egg seventeen days after the removal 

 of the male. Townsley and Philips results are shown in 

 Table XIV. 



Sherwood' reports one Barred Plymouth Rock hen that 

 produced one fertile egg on the twentieth day after the mating 

 was broken up; four White Leghorn pullets that produced 

 fertile eggs on the nineteenth day; two Leghorn hens that 

 laid fertile eggs on the eighteenth day after the male bird 

 was removed. He found that the fertility held up well with 

 the Plymouth Rock hens for twelve days, while the Leghorn 

 pullets' eggs decreased markedly in fertility on the tenth 

 day, as did also those of the Leghorn hens. 



After the end of the third week, according to Lillie,* the 

 vitality of the spermatozoa is reduced. Eggs laid during 

 the fourth and fifth week after the removal of the male 

 may exhil)it an abnormal cell division, wdiich soon ceases. 



In practice a period of at least three weeks is necessary 

 to rid the oviduct of active spermatozoa and insure a cessa- 

 tion of the influence of a previous mating. 



Influence of Previous Impregnation. — The fact that eggs 

 remain fertile for days and even weeks after the removal 

 of the male, combined with other circumstances, has led 

 to a somewhat common belief that the influence of an impreg- 

 nation is often permanent. A common illustration is found 

 in the idea that if a pure white hen is once mated with a pure 

 black male the offspring of a subsequent mating with a pure 

 white male, which may occur the following season or even 

 two or three years later, are likely to show blacj^ feathers, 

 as the result of the previous mating with the black male. 



As a matter of fact, black feathers are a frequent occur- 

 rence in the offspring of pure white birds that have n.ever 



' Maryland BiiUctin No l.'w 



^ Unpublished data, Iowa Sprite Conpij;e. 



' Ibid., Ohio Experiment Slulion. 



^ Development of tlio Chick. 



