BILATERALITY OF THE PIGEON's EGG 291 



16.7 by 14.7 by 16.3 mm. The details of this final period of 

 rapid yolk secretion have been described by Loyez ('05-6), Riddle 

 Cll) and others; suffice it to say, that the yolk is laid down con- 

 centrically so that the long axis is preserved and the latebra retains 

 its eccentric position. Figure 38 shows the conditions in an oocyte 

 twenty-four hours before ovulation; the end of the long axis 

 which was directed toward the cloaca is toward the right and it 

 is obvious that the latebra is nearer the other, 'infundibular' 

 end. In oviducal eggs the outlines are no longer so clear and often 

 the eccentricity of the latebra is only represented by an extension 

 toward the infundibular end of the long axis as is shown in figure 

 39 which is the cut median surface of an oviducal egg (see also 

 description of the figures). In laid eggs the softening of the 

 yolk and transfusions make the relations much less distinct than 

 in the earlier stages. 



2, Correlations in the reproductive apparatus. As has been said 

 usually but two oocytes enter upon the final growth period 

 together. Shortly after the initial stimulus has been received 

 in the ovary, the oviduct becomes highly vascular and increases 

 in size. In one bird that was studied the larger follicle was 9.1 mm., 

 less than one-half the definitive size, the oviduct with its fim- 

 briated infundibulum was about one-fourth the maximal size and 

 both funnel and glandular oviduct were in peristalsis. In another 

 instance, where the larger follicle was 13.2 mm. (in long axis), 

 the second 8.2 mm. the oviduct was almost full size and the active 

 funnel was wrapped about the larger follicle. The correlation of 

 ovarian and oviducal activities is presumably due to the presence 

 of the internal secretion of the ovary in the circulation. It may 

 be said in this connection that the interstitial cells of the ovary 

 show much greater signs of activity in functioning ovaries than 

 they do in ovaries from birds that had not laid for a long time. 



The whole reproductive mechanism is delicately balanced and 

 there are interesting physiological problems here still to be worked 

 out. How is it, for example, that the funnel is attracted to the 

 follicle, and that it, eventually, always clasps the larger one, 

 though in the early stages of the final growth period it may, rarely, 

 be found about the smaller? What determines that usually but 

 two follicles mature at a time and that never more than two 



