2O4 MAYNIE R. CURTIS. 



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 within another egg is not usually im- 

 mediately 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. 



Q. 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 appli- 

 cation 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 down- 

 wardly directed stimulus. 



n. 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 phe- 

 nomena 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 eggs 

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

 or enclosed wdthin 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 direc- 

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

 and shell. This backward movement must cease before the 

 egg is expelled from the funnel mouth and the movement 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 



