292 GEORGE W. BARTELMEZ 



eggs are laid? How comes it that yolk secretion, and other 

 factors are so regulated that ovulation is closely correlated with 

 the nuclear maturation phenomena? 



To discuss ovulation and the method of orientation it will be 

 necessary first to consider the relation between mature follicle 

 and oviduct. If the reproductive apparatus of a bird be studied 

 two to twenty-four hours before the rupture of the first follicle 

 is due, the following conditions are found : Oviduct and funnel are 

 in active peristalsis, the latter is closely wrapped about the larger 

 follicle, endeavoring so to speak, to swallow it. Under such con- 

 ditions the follicle is obviously oriented along lines of least resist- 

 ance, and accordingly its long axis coincides with that of the 

 oviduct and approximately with antero-posterior axis of the bird. 

 One end of the long axis of the follicle is therefore directed 

 posteriorly, toward the cloaca, and this may be termed the 

 cloacal end of the egg. It will be remembered that, in the 

 incubated egg, the cloacal end of the egg is definitely related to 

 the head of the embryo (diagram I, p. 275) and since the antero- 

 posterior axis of the embryo is determined before ovulation, it 

 follows, when the method of orientation and ovulation is taken 

 into account, that this cloacal end of the long axis is predeter- 

 mined in the ovary. Figure 36 is from a ventral view of a pair 

 of foUicles about twenty-four hours before ovulation. In the 

 larger one the stigma appears in the long axis of the follicle, and 

 the long axis extends antero-posteriorly with reference to the 

 bird. The funnel (inf.) contracted in preservation and is seen 

 on the left side of the bird. 



How comes it that one end of the long axis is found nearer the 

 cloaca? The explanation appears when a mature follicle is 

 removed from the bird and suspended at the center of the animal 

 pole in an albumen solution of the density of that which fills 

 the body cavity at the time of ovulation ; it is found that one end 

 of the follicle is heavier than the other, and this is due to the 

 eccentricity of the latebra (fig. 38) whose position nearer the 

 infundibular end of the long axis is due, as will be remembered, 

 to the corresponding position of the germinal vesicle in the early 

 stages. The cloacal end of the ovum, i.e., the end which goes 



