Feb. 15, 191S Simultaneous Ovulaiion and Double- Yolked Eggs 



577 



(A), where the chalazal membrane and chalazas are probably secreted, 

 and the albumen-secreting portion (B). There is, however, a difference 

 in the general appearance of the glandular ridges and the microscopic 

 character of the glands for a distance of 5 to 8 cm. in an adult laying 

 barred plymouth rock fowl. There is a definite Une of demarcation, 

 the isthmus ring (x) , where the egg membrane begins to be secreted. The 

 length of the duct from the mouth of the funnel to the isthmus ring has 

 been determined for 57 normal laying barred plymouth rock fowls. The 

 mean length was 46.3 cm. 



The portion of the oviduct in which two yolks can unite and have all the 

 egg envelopes common is probably within the length of the funnel — that 

 is, from 5 to 8 cm. The portion where they will have all their envelopes 

 separate, except the egg membrane and shell, probably roughly approxi- 

 mates the length of the first egg when passing into the isthmus, or from 

 5 to 7 cm. The union of two eggs in any other part of the duct from the 

 ostium to the isthmus ring (30 to 35 cm.) would result in the formation 

 of a double-yolked egg with all or part of the thick albumen common to 

 both yolks. If we take as the means of the above figures 7, 33, and 6 cm. 

 and calculate the percentage that each is of the total length from ostium 

 to isthmus ring we shall have the expected percentage of double-yolked 

 eggs of each type, if the probability of the union of two yolks is equal at 

 every level of the duct. The number and percentage of eggs of each type 

 observed and the number and percentage expected on the above assump- 

 tion are given in Table I. 



Table I. — Number and percentage observed of each type of double-yolked eggs and the 

 number and percentage expected, if there is an equal probability of the union of the two 

 components at every level of the oviduct 



The close agreement between the data for the eggs obser\-cd and 

 those expected in each type supports the conclusion that the union of 

 the component eggs occurs indiscriminately at all levels of the oviduct. 

 While the eggs observed formed a graded scries and the divisions of 

 the duct are somewhat rough, nevertheless, variations in classification 

 within any possible range of observation could not reverse the conclusion 

 that the short distances of duct which could yield eggs of the first and 



