PHYSIOLOGY OF REPRODUCTION IN DOMESTIC FOWL. 63 



produced by the holding of the first egg in the duct after it would 

 normally be laid. 



A few cases of egg-bound birds have come to autopsy in which 

 the uterus contained a second fully mature egg. These cases 

 do not of course necessarily indicate an unusually rapid egg 

 production. One case, however, came to autopsy where there 

 were two normal thin shelled eggs in the uterus. Neither one 

 seemed to have the shell completely formed. There was no 

 evidence that the eggs could not be laid. This appeared to be a 

 case where two eggs were being completed at the same time. The 

 bird had never laid. 



These cases have been described because it seems clear that 

 the kind of disturbances which cause the production of eggs with 

 more than one yolk may also, when slighter in extent or when 

 localized in a more posterior portion of the oviduct, cause other 

 irregularities in egg production. 



There is in fact a certain type of abnormal egg which forms 

 the logical step between two eggs at one time and the double- 

 yolked egg. Such eggs, although occurring very infrequently, 

 have several times been described in poultry journals. One of 

 them has been produced at this plant. These abnormalities 

 consist of pairs of normal eggs united by a tube of membrane 

 containing albumen. In the pair of such eggs produced at this 

 plant the components were both soft shelled, one of them having 

 a little more shell than the other. In such cases the second egg 

 must have so nearly approached the first that the stimuli upon 

 the isthmus glands overlapped, causing the formation of the 

 membranous tube continuous with the shell membrane of each. 

 It is interesting to note that the bird which produced this egg 

 had produced a double-yolked egg six days before. Mr. F. E. 

 Field, 1 of Birmingham, England, who described and published a 

 photograph of such an egg, also notes that the pullet which pro- 

 duced it "has since laid several double-yolked eggs." The 

 relation between such eggs and certain types of double-yolked 

 eggs is obvious. If the second egg actually overtakes the first 

 before the first has completely entered the isthmus a double- 



1 Field, F. E., "Peculiar Twin Eggs," Poultry World (London), Vol. II., N.S., 

 pp. 1152, 1913. 



