SOMATIC AND GENETIC STERILITY 59 



SUMMARY 



1. Birds which are hereditarily high layers may fail to make 

 good performance records because for some anatomical reason 

 it is impossible for yolks to enter the oviduct. 



2. Birds which ovulate, or return partly-formed eggs, into the 

 body cavity usually show the nesting instinct. 



3. The nesting records show a rhythm similar to egg records 

 of normal birds and it seems probable that they are the normal 

 resultant of the ovulation, v 



4. Data given in this paper also confirm the following state- 

 ments made in a recent paper (Pearl and Curtis '14) : 



a. In case of stoppage of the duct at any level, the duct on 

 both sides of the point of stoppage passes through the same 

 cyclic changes, coordinated with the cyclic changes in the ovary, 

 as a normal unobstructed duct. The duct functions only as 

 far as it receives the stimulus of the advancing egg. 



b. Absence of pressure from the funnel does not prevent or 

 apparently greatly retard ovulation. Increased internal pres- 

 sure may therefore be the most important factor in normal 

 ovulation. 



c. Yolks of partly or fully formed eggs may be absorbed rapidly 

 and in large numbers from the peritoneal surface without caus- 

 ing any serious derangement of normal metabolic processes. 



LITERATURE CITED 



Patterson, J. T. 1910 Studies in the earl}' development of the hen's egg. 



I. History of early cleavage and accessory cleavage. Jour. Morph., 



vol. 21, pp. 101-134. 

 Pearl, R. 1911 On the accuracy of trap-nest records. Ann. Rept. Maine 



Agr. Expt. Stat, for 1911, pp. 186-193. 



1912 The mode of inheritance of fecundity in the domestic fowl. 



Jour. Exp. Zool., vol. 13, pp. 153-268. 

 Pearl, R., and Curtis, M. R. 1914 Studies on the physiology of reproduction 



in the domestic fowl. VIII. On some physiological effects of ligation, 



section or removal of the oviduct. Jour. Exp. Zool., vol. 17, pp. 395- 



424. 



