THE BREEDING OF CHICKENS S9 



way (liss(.)l\'('s some of tlie denser alhuinen aJi'eady present, 

 and so brings about the dilution of the hitter in some degree. 

 At tlie same time i)y tliis proeess of diii'usion, tlie liuid hiyer 

 is rendered more dense, coming finally to the eonsisteney of 

 the thin layer of the laid egg. The thhi albumen lajer, how- 

 ever, does not owe its existence in any sense to this dilution 

 factor, but to a definite secretion of a thin allnmien by the 

 glands of the isthmus and uterus. The addition of albumen 

 to the egg is comi)leted only after it has been in the uterus 

 from five to seven hours. 



" Before the acquisition of albiunen by the egg is completed 

 a fairly ctmsiderable amount of shell substance has been 

 deposited on the shell membranes. For the completion of the 

 shell and the laying of the egg from twelve t<.) sixteen, or 

 exceptionally even more, hoiu's are refpiired."' 



It is while the egg is in the uterus that it is jxissible to 

 locate it by touch. ±\t the I'tah Station- this fact lias been 

 nuule use of in kecjiing egg records except during tlie breeding 

 season when ])edigreeing is being done. It was found tliat 

 the whole fiock could be handled early each morning and the 

 in(li\idual hens wliich would lay that day, determined with 

 accuracy. 



Curtis' has shown that the larger an egg, the greater is 

 the mechanical stimulation upon the uterus and the heavier is 

 the shell. 



Infertile Eggs. — The discharging of the yolk or ovum from 

 the o\ary of the hen is analogous to ovulation in other farm 

 animals. 



With the larger animals, if o^'ulation is not followed by 

 mating, there is no further development. With birds, 

 howe\er, whether the ovum is fertilized in the fuimel of the 

 oviduct by union with the male element or not, its further 

 history within the hen's l)ody is the same and an apparently 

 normal egg is laid. If the hen has not been pre\iously mated 

 and there are no spermatozoa in the o\'iduct to unite with 

 the ovum, the egg is called infertile and will not start to 



' Pearl and Curtis, Jourzial Experimeotal Zooloiiy, vol. xii. No. 1 

 - Jour. Am. As?n. Inst, and In\-('st. in I'oul. Hu^li., v(.i. lii. No. 9. 

 3 Maine Bulletin No. 228. 



