REPRODUCTION IN THE DOMESTIC FOWL. 



191 



shell gland at autopsy or have been found partly extruded from 

 the cloaca in cases of egg-bound birds. However, we have 

 observed a few cases where the egg in the shell gland or partly 

 extruded was blunt end caudad. Moreover, a series of obser- 

 vations carried on at this laboratory confirm Bonnet's (l) 

 statement that the pointed end of the egg is usually laid first 

 but that occasionally the blunt end comes out first. 

 Since so far as we know the egg is always formed with its 

 pointed end caudad but is sometimes laid blunt end first it seems 

 probable that in the latter cases the egg turns in the duct. 

 In this connection the results of some rough preliminary experi- 

 ments in an investigation of the mechanism of laying are of 

 interest. During routine autopsy work hard-shelled eggs found 

 in the shell gland were forced out by pressure from behind. 

 Usually the eggs passed directly backward and out pointed end 



FIG. 5. Diagram showing an egg in the shell gland. D.L. = Dorsal liga- 

 ment; E = egg; / = isthmus; S = shell gland; V = vagina; V.L. = ventral 

 ligament. 



first, but several times the pointed end turned dorsad and the 

 egg reversed ends. Continued pressure then forced the egg out 

 blunt end first. Fig. 5 shows a diagram of the egg in the uterus. 

 If pressure is so applied that the pointed end is pressed directly 

 into the opening of the vagina or ventral to it on the thin fold 

 the egg comes out pointed end first. However, if it is pressed 

 against the uterine wall slightly dorsal to the vaginal opening, 

 the point slips along this curved caudodorsal angle of the uterus 



