350 MAINE AGRICULTURAL EXPERIMENT STATION. I916. 



8. A hard-shelled egg uncovered by membrane or albumen 

 is sometimes found in the body cavity or upper oviduct while 

 a hard-shelled egg enclosed with another egg is not usually 

 immediately surrounded by an egg membrane. It would, there- 

 fore, seem that the egg does not cause the secretion of egg 

 envelopes around itself on its way up the duct. 



9. Since in the case of a double-yolked egg a second yolk 

 closely following the first does stimulate the secretion of the 

 successive envelopes, it does not seem probable that the failure 

 of the duct to form envelopes around the returning egg is due 

 to exhaustion of the glands. 



10. The reason for this failure is not known. It may be 

 that the return of the egg is very rapid and that the time of 

 application of the stimulus is too short to be effectual, or there 

 may be a real polarity of the duct so that it responds only to a 

 downwardly directed stimulus. 



11. A few cases are known where one or more of the 

 normal egg envelopes have not been formed around an egg 

 advancing in the normal direction (for example, a yolk enclosed 

 by egg membrane and shell but with no albumen, or a laid egg 

 composed only of normal yolk and albumen). The cause for 

 these phenomena are not known. In these cases the movement 

 of the egg may have been abnormally rapid. 



12. The occurrence of membrane-covered or hard-shelled 

 egg9 in the body cavity, the albumen-secreting region of the 

 oviduct or enclosed within the albumen of another egg shows 

 that an egg may be moved up the duct, but since an egg has 

 never been observed moving in this direction the nature of the 

 motion can only be imagined. 



13. The double egg results from a modification of the 

 normal processes of egg formation due chiefly to a reversal in 

 the direction of the egg after it has received its membrane or 

 its membrane and shell. The backward movement must cease 

 before the egg is expelled from the funnel mouth and the move- 

 ment in the normal direction must be resumed. 



14. If the backward movement sets in before the egg 

 receives its membrane but stops before it is expelled from the 

 funnel mouth and if the normal direction is then resumed, the 

 result will be a normal egg with a large percentage of albumen 



